JP7650174B2 - Lubricating oil composition for internal combustion engines - Google Patents

Description

The present invention relates to a lubricating oil composition for internal combustion engines.

In recent years, with the increasing performance and power output of internal combustion engines such as automobile engines, high performance is required for lubricants (engine oils) for internal combustion engines, and various lubricant compositions in which various additives are blended with lubricant base oils are being researched.

For example, International Publication No. 2019/221295 (Patent Document 1) discloses a lubricating oil composition for internal combustion engines, which comprises a lubricating oil base oil, (A) a metal-based detergent containing calcium borate, and (B) a metal-based detergent containing magnesium, in which the (A) component is one or more calcium-based detergents overbased with calcium borate, or a combination of one or more calcium-based detergents overbased with calcium borate and one or more calcium-based detergents not overbased with calcium borate, and in which the molar ratio B/Ca of the total boron content B (unit: mol) derived from the metal-based detergent in the lubricating oil composition to the total calcium content Ca (unit: mol) derived from the metal-based detergent in the lubricating oil composition is 0.52 or more.

In addition, International Publication No. 2018/212340 (Patent Document 2) discloses a lubricating oil composition for internal combustion engines that contains a lubricating oil base oil, (A) a metal-based detergent containing calcium borate, and (B) a metal-based detergent containing magnesium. Paragraph [0064] of the same document discloses that the molar ratio B/Ca of the total boron content B (unit: mol) derived from the metal-based detergent in the lubricating oil composition to the total calcium content Ca (unit: mol) derived from the metal-based detergent in the lubricating oil composition is preferably 0.52 or more.

Furthermore, JP 2017-226793 A (Patent Document 3) discloses a lubricating oil composition for internal combustion engines that contains (A) a lubricating base oil and (B) a metal-based detergent that contains (B1) a calcium-containing metal-based detergent and (B2) a magnesium-containing metal-based detergent, with the calcium amount being 500 to 2500 ppm by mass and the magnesium amount being 100 to 1000 ppm by mass based on the total amount of the composition.

International Publication No. 2019/221295 International Publication No. 2018/212340 JP 2017-226793 A

However, even with the conventional lubricating oil compositions for internal combustion engines described in Patent Documents 1 to 3, there was room for improvement in terms of improving the performance of suppressing LSPI [Low Speed Pre-Ignition] (LSPI suppression ability) while also improving friction performance to simultaneously improve fuel efficiency.

The present invention was made in consideration of the problems associated with the above-mentioned conventional technology, and aims to provide a lubricating oil composition for internal combustion engines that is capable of achieving both excellent LSPI suppression capability and excellent fuel economy performance.

As a result of intensive research conducted by the present inventors in order to achieve the above-mentioned object, the present inventors have discovered that a lubricating oil composition for internal combustion engines contains (A) a lubricating base oil and (B) a metal-based detergent; said component (B) contains (B1) a calcium-based detergent having a calcium content in the range of 1650 ppm by mass or more and 2500 ppm by mass or less, based on the total mass of the composition, and (B2) a magnesium-based detergent having a magnesium content in the range of 20 ppm by mass or more and 400 ppm by mass or less, based on the total mass of the composition; said component (B1) contains (B1-1) a calcium-based detergent containing boron and calcium; the boron content, based on the total mass of the composition, is 1000 ppm by mass or less; and further, the content (mass ratio) of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , and the content (mass ratio) of calcium in component (B1) based on the total mass of the composition is represented as Ca(B1). The inventors have found that, when the content (mass ratio) of magnesium in component ₍ B2) based on the total mass of the composition is expressed as Mg _(B2) , the ratio of B _(B1) to Ca( _B1) (B _(B1) /Ca _(B1) ) is 0.15 or more and 0.35 or less, and the ratio of B _{(B1) to the total amount of Ca(B1) and Mg( B2} ) (Ca( _B1) +Mg _(B2) ) (B _(B1) /[Ca _(B1) +Mg _(B2) ]) is 0.13 or more and 0.29 or less, the LSPI suppression ability of the lubricating oil composition for internal combustion engines can be made excellent, and friction performance can be improved to simultaneously make the fuel saving performance excellent, which has led to the completion of the present invention.

That is, the lubricating oil composition for internal combustion engines of the present invention has
(A) a lubricating base oil , ( B) a metal-based detergent , and (G) an antiwear agent ;
The component (B) is
(B1) a calcium-based detergent having a calcium content of 1,750 ppm by mass or more and 2,000 ppm by mass or less based on the total mass of the composition;
(B2) a magnesium-based detergent having a magnesium content in the range of 20 ppm by mass or more and 150 ppm by mass or less based on the total mass of the composition;
Contains
The component (B1) contains (B1-1) a calcium-based detergent containing boron and calcium,
The component (G) is a phosphorus-based antiwear agent containing zinc,
The boron content based on the total mass of the composition is 500 ppm by mass or more and 650 ppm by mass or less ,
The phosphorus content based on the total mass of the composition is 700 ppm by mass or more and 800 ppm by mass or less,
where the content of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , the content of calcium in component (B1) based on the total mass of the composition is represented as Ca _(B1) , and the content of magnesium in component (B2) based on the total mass of the composition is represented as Mg _(B2) , the ratio of B _(B1) to Ca _(B1 ) (B _(B1) /Ca _(B1) ) is 0.15 or more and 0.30 or less, and the ratio of B _{(B1) to the total amount of Ca(B1)} and Mg _(B2) (Ca _(B1) +Mg _(B2) ) (B( _{B1 )} /[Ca _(B1) +Mg _(B2) ]) is 0.13 or more and 0.29 or less,
In the descriptions in this specification, "the boron content in component (B1) based on the total mass of the composition,""the calcium content in component (B1) based on the total mass of the composition," and "the magnesium content in component (B2) based on the total mass of the composition," the term "content" refers to the mass ratio based on the total mass of the composition (total amount of the composition) (mass ratio: content ratio based on mass).

In the lubricating oil composition for internal combustion engines of the present invention, it is preferable that the component (B1) contains calcium borate salicylate as the component (B1-1).

The internal combustion engine lubricating oil composition of the present invention preferably further contains (C) a poly(meth)acrylate-based viscosity index improver. The (C) component preferably contains a comb-type poly(meth)acrylate-based polymer.

The present invention makes it possible to provide a lubricating oil composition for internal combustion engines that is capable of exhibiting both excellent LSPI suppression ability and excellent fuel economy performance.

The present invention will be described in detail below with reference to preferred embodiments. In this specification, unless otherwise specified, the expression "X to Y" for numerical values X and Y means "X or more and Y or less." In such expressions, when a unit is added only to numerical value Y, the unit is also applied to numerical value X.

The lubricating oil composition for internal combustion engines of the present invention comprises:
(A) a lubricating base oil; and (B) a metal-based detergent.
The component (B) is
(B1) a calcium-based detergent having a calcium content in the range of 1650 ppm by mass or more and 2500 ppm by mass or less based on the total mass of the composition;
(B2) a magnesium-based detergent having a magnesium content in the range of 20 ppm by mass or more and 400 ppm by mass or less based on the total mass of the composition;
Contains
The component (B1) contains (B1-1) a calcium-based detergent containing boron and calcium,
The boron content based on the total mass of the composition is 1000 ppm by mass or less;
where the content (mass ratio) of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , the content (mass ratio) of calcium in component (B1) based on the total mass of the composition is represented as Ca _(B1) , and the content (mass ratio) of magnesium in component (B2) based on the total mass of the composition is represented as Mg _(B2) , the ratio of B _{(B1) to Ca(B1 )} (B _(B1) /Ca _(B1) ) is 0.15 or more and 0.35 or less, and the ratio of B(B1) to the total amount of Ca _(B1) and Mg _(B2) (Ca _(B1) +Mg( _{B2 )} ) (B _(B1) /[Ca _(B1) +Mg _(B2) ]) is 0.13 or more and 0.29 or less,
First, each component that may be contained in the lubricating oil composition for internal combustion engines of the present invention will be described below.

<(A) Component: Lubricating base oil>
The lubricating base oil used as component (A) in the present invention is not particularly limited, and any known base oil available in the field of lubricating oils can be used as appropriate. For example, one or more mineral base oils, or one or more synthetic base oils, or a mixture thereof can be used.

As the mineral base oil usable as the lubricating base oil, in the classification of base oils by API (American Petroleum Institute), Group II base oil, Group III base oil, Group IV base oil, Group V base oil, or a mixture of two or more of these base oils (mixed base oil) can be suitably used (hereinafter, the group of base oil classification by API will be simply referred to as "API group"). Here, API Group II base oil is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturate content of 90 mass% or more, and a viscosity index of 80 or more and less than 120. API Group III base oil is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturate content of 90 mass% or more, and a viscosity index of 120 or more. API Group IV base oil is a poly-α-olefin base oil. Furthermore, API Group V base oils are base oils other than API Groups I to IV, and preferred examples include ester-based base oils.

As mineral oil base oils, for example, paraffinic mineral oils obtained by refining lubricating oil fractions obtained by atmospheric and/or vacuum distillation of crude oil through one or a combination of two or more refining processes selected from the group consisting of solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, as well as normal paraffinic base oils, isoparaffinic base oils, and mixtures thereof can be used.

Preferred examples of mineral base oils include base oils obtained by using the following base oils (1) to (8) as raw materials, refining the raw material oil and/or a lubricating oil fraction recovered from the raw material oil by a predetermined refining method, and recovering the lubricating oil fraction.
(1) Distillate oil obtained by atmospheric distillation of paraffinic and/or mixed crude oils (2) Distillate oil obtained by vacuum distillation of residual oil obtained by atmospheric distillation of paraffinic and/or mixed crude oils (WVGO)
(3) Wax obtained by a lubricant dewaxing process (slack wax, etc.) and/or synthetic wax obtained by a gas-to-liquid (GTL) process, etc. (Fischer-Tropsch wax, GTL wax, etc.)
(4) One or more mixed oils selected from the base oils (1) to (3) and/or mild hydrocracking treated oils of the mixed oils; (5) Two or more mixed oils selected from the base oils (1) to (4); (6) Deasphalted oil (DAO) of the base oils (1), (2), (3), (4) or (5).
(7) Mild hydrocracking treated oil (MHC) of base oil (6)
(8) A mixed oil of two or more types selected from the base oils (1) to (7).

The above-mentioned specified refining methods are preferably hydrorefining such as hydrocracking and hydrofinishing; solvent refining such as furfural solvent extraction; dewaxing such as solvent dewaxing and contact dewaxing; clay refining using acid clay or activated clay; and chemical (acid or alkali) washing such as sulfuric acid washing and caustic soda washing. One of these refining methods may be carried out alone, or two or more may be combined. When two or more refining methods are combined, the order is not particularly limited and can be selected as appropriate.

As the mineral base oil, the following base oil (9) or (10) obtained by subjecting a lubricating oil fraction recovered from the base oil selected from the above base oils (1) to (8) or a predetermined treatment, is particularly preferred.
(9) A hydrocracked base oil obtained by hydrocrack- ing a base oil selected from the base oils (1) to (8) or a lubricating oil fraction recovered from the base oil, and subjecting the product or the lubricating oil fraction recovered from the product by distillation or the like to a dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or by distilling the dewaxing treatment after the hydrocracked base oil (10) A hydroisomerized base oil obtained by hydroisomerizing a base oil selected from the base oils (1) to (8) or a lubricating oil fraction recovered from the base oil, and subjecting the product or the lubricating oil fraction recovered from the product by distillation or the like to a dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or by distilling the dewaxing treatment after the hydroisomerized base oil. Note that the lubricating oil base oils of (9) and (10) are each more preferably produced through a catalytic dewaxing treatment (step) as a dewaxing treatment. In addition, when obtaining the lubricating oil base oil of (9) or (10), a solvent refining treatment and/or a hydrofinishing treatment step may be further carried out at an appropriate stage as necessary.

The % C _P of the mineral base oil is preferably 70 to 99, more preferably 70 to 95, even more preferably 75 to 95, and particularly preferably 75 to 94. When the % C _P of the base oil is equal to or greater than the lower limit, it is possible to improve the viscosity-temperature characteristics and further improve the fuel economy performance. In addition, when an additive is blended into the base oil, it is possible for the additive to fully exert its effect. In addition, when the % C _P of the base oil is equal to or less than the upper limit, it is possible to increase the solubility of the additive.

The % _CA of the mineral base oil is preferably not more than 2, more preferably not more than 1, even more preferably not more than 0.8, and particularly preferably not more than 0.5. By having the % _CA of the base oil be equal to or less than the upper limit, it becomes possible to improve the viscosity-temperature characteristics and further improve the fuel economy performance.

The % C _N of the mineral base oil is preferably 1 to 30, more preferably 4 to 25. By having the % C _N of the base oil be equal to or less than the upper limit, it is possible to improve the viscosity-temperature characteristics and further improve the fuel saving performance. Also, by having the % C _N be equal to or more than the lower limit, it is possible to increase the solubility of additives.

In this specification, %C _P , %C _N and %C _A respectively mean the percentage of paraffin carbon number to the total carbon number, the percentage of naphthene carbon number to the total carbon number and the percentage of aromatic carbon number to the total carbon number, which are determined by a method (nd-M ring analysis) in accordance with ASTM D 3238-85. In other words, the preferred ranges of the above-mentioned %C _P , %C _N and %C _A are based on the values determined by the above-mentioned methods, and for example, even in the case of a lubricating base oil that does not contain naphthene content, the %C _N determined by the above-mentioned method may show a value exceeding 0.

The content of saturated matter in the mineral oil-based base oil is preferably 90% by mass or more, preferably 95% by mass or more, and more preferably 99% by mass or more, based on the total amount of the base oil. By having the content of saturated matter equal to or more than the lower limit, it is possible to improve the viscosity-temperature characteristics. In this specification, saturated matter means a value measured in accordance with ASTM D 2007-93.

In addition, a similar method that can obtain similar results can be used to separate the saturates. For example, in addition to the method described in ASTM D 2007-93, the method described in ASTM D 2425-93, the method described in ASTM D 2549-91, a method using high performance liquid chromatography (HPLC), or an improvement of these methods can be used.

The aromatic content in the mineral oil-based base oil is preferably 0 to 10 mass%, more preferably 0 to 5 mass%, particularly preferably 0 to 1 mass%, based on the total amount of the base oil, and in one embodiment, may be 0.1 mass% or more. By having the aromatic content be equal to or less than the upper limit, it is possible to improve the viscosity-temperature characteristics and low-temperature viscosity characteristics, further improve the fuel-saving performance, and reduce the evaporation loss of the lubricating oil to reduce the consumption of the lubricating oil. In addition, it is possible to effectively exert the effect of the additives blended in the lubricating oil. In addition, the lubricating oil base oil may not contain aromatic content, but by having the aromatic content be equal to or more than the lower limit, the solubility of the additives can be increased. In this specification, the aromatic content means a value measured in accordance with ASTM D 2007-93. Aromatic components typically include alkylbenzenes, alkylnaphthalenes, anthracene, phenanthrene and their alkylated derivatives, as well as compounds with four or more condensed benzene rings, pyridines, quinolines, phenols, naphthols and other aromatic compounds with heteroatoms.

The synthetic base oil that can be used as the lubricating oil base oil is not particularly limited, and known synthetic base oils can be used as appropriate. Examples of such synthetic base oils include poly-α-olefins and their hydrogenated products, isobutene oligomers and their hydrogenated products, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, bis-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, bis-2-ethylhexyl sebacate, etc.), polyol esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycols, dialkyl diphenyl ethers, polyphenyl ethers, and mixtures thereof. Among these, poly-α-olefin base oils are preferred. Typical examples of poly-α-olefin base oils include oligomers or co-oligomers of α-olefins having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) and their hydrogenated products.

The lubricating base oil preferably has a kinetic viscosity at 100°C of 2.0 to 5.0 ^mm2 /s (more preferably 3.0 to 5.0 ^mm2 /s, even more preferably 4.0 to 4.8 ^mm2 /s, and particularly preferably 4.1 to 4.7 ^mm2 /s). When the kinetic viscosity at 100°C of the lubricating base oil is equal to or greater than the lower limit, it is possible to form an oil film efficiently at the lubricating points, and to reduce the evaporation loss of the lubricating oil composition and reduce the consumption of the lubricating oil, compared with the case where the kinetic viscosity is less than the lower limit. In addition, when the kinetic viscosity at 100°C of the lubricating base oil is equal to or less than the upper limit, it is possible to achieve even better fuel saving performance, compared with the case where the kinetic viscosity exceeds the upper limit. In this specification, the term "kinetic viscosity at 100°C" refers to the kinetic viscosity at 100°C measured in accordance with JIS K 2283-2000.

The lubricating base oil preferably has a kinetic viscosity at 40°C of 9.0 to 36.0 ^mm2 /s (more preferably 12.6 to 33.2 ^mm2 /s, even more preferably 15.8 to 25.2 ^mm2 /s, particularly preferably 17.7 to 21.6 ^mm2 /s, and most preferably 17.5 to 22.1 ^mm2 /s). When the kinetic viscosity at 40°C of the lubricating base oil is equal to or less than the upper limit, the low-temperature viscosity characteristics and fuel-saving performance of the lubricating oil composition can be further improved compared to when the kinetic viscosity exceeds the upper limit. When the kinetic viscosity at 40°C of the lubricating base oil is equal to or more than the lower limit, the lubricating properties can be improved by improving the oil film forming properties at the lubricating points, and the evaporation loss of the lubricating oil composition can be reduced, thereby reducing the consumption of the lubricating oil. In this specification, the term "kinematic viscosity at 40° C." means the kinematic viscosity at 40° C. measured in accordance with JIS K 2283-2000.

The lubricating base oil preferably has a viscosity index of 100 or more (more preferably 105 or more, even more preferably 110 or more, particularly preferably 115 or more, and most preferably 120 or more). When the viscosity index is equal to or greater than the lower limit, it is possible to improve the viscosity-temperature characteristics and anti-wear properties of the lubricating oil composition, as well as to further improve fuel economy performance, compared to when the viscosity index is less than the lower limit. Furthermore, it is possible to reduce evaporation loss of the lubricating oil, thereby reducing the amount of lubricating oil consumed. In this specification, "viscosity index" refers to a viscosity index measured in accordance with JIS K 2283-1993.

The lubricating base oil preferably has a NOACK evaporation amount of 30% by mass or less (more preferably 15% by mass or less) at 250°C. The lower limit of the NOACK evaporation amount of the lubricating base oil at 250°C is not particularly limited, but is usually 3% by mass or more. In this specification, the "NOACK evaporation amount at 250°C" refers to the evaporation amount of the lubricating base oil or lubricating oil composition at 250°C measured in accordance with ASTM D 5800.

The lubricating base oil preferably has a pour point of -10°C or less (more preferably -12.5°C or less, and even more preferably -15°C or less). When the pour point is equal to or less than the upper limit, it is possible to improve the low-temperature fluidity of the entire lubricating oil composition compared to when the pour point exceeds the upper limit. In this specification, "pour point" means the pour point measured in accordance with JIS K 2269-1987.

The sulfur content of the lubricating base oil depends on the sulfur content of the raw material. For example, when a raw material that is substantially free of sulfur, such as a synthetic wax component obtained by a Fischer-Tropsch reaction, is used, a lubricating base oil that is substantially free of sulfur can be obtained. In this specification, "sulfur content" means the sulfur content measured in accordance with JPI-5S-38. In addition, when a raw material containing sulfur, such as slack wax obtained in the refining process of the lubricating base oil or micro wax obtained in the refined wax process, is used, the sulfur content of the obtained lubricating base oil is usually 100 ppm by mass or more. From the viewpoint of reducing sulfur in the lubricating oil composition, the sulfur content of the lubricating base oil is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, even more preferably 10 ppm by mass or less, and particularly preferably 5 ppm by mass or less.

The nitrogen content in the lubricating base oil is preferably 10 ppm by mass or less (more preferably 5 ppm by mass or less, and even more preferably 3 ppm by mass or less). In this specification, nitrogen content refers to the nitrogen content measured in accordance with JIS K 2609-1990.

The content of lubricating base oil (total base oil) in the lubricating oil composition is preferably 70 to 95 mass % (more preferably 75 to 85 mass %) based on the total mass of the composition.

<Component (B): Metal-Based Detergent>
The metallic detergent used as component (B) in the present invention is
(B1) a calcium-based detergent having a calcium content based on the total mass of the composition (the calcium content derived from component (B1) based on the total mass of the composition) in the range of 1650 ppm by mass or more and 2500 ppm by mass or less;
(B2) a magnesium-based detergent having a magnesium content based on the total mass of the composition (the magnesium content derived from component (B2) based on the total mass of the composition) in the range of 20 ppm by mass or more and 400 ppm by mass or less;
It comprises:

Here, the term "calcium-based detergent" refers to a metal-based detergent containing calcium as the metal, and the term "magnesium-based detergent" refers to a metal-based detergent containing magnesium as the metal. As such a metal-based detergent, it is sufficient to appropriately select and use from among known metal-based detergents (for example, sulfonate detergents, phenate detergents, salicylate detergents, etc. containing calcium or magnesium as the metal) so that the amounts of calcium, magnesium, and boron are each in the desired content ratio. Here, examples of the "sulfonate detergents," "phenate detergents," and "salicylate detergents" exemplified as known metal-based detergents include those described in paragraphs [0038] to [0054] of JP 2020-76004 A and those described in paragraphs [0043] to [0054] of WO 2018/212340 A, etc., can be appropriately used.

Regarding component (B1):
The "calcium-based detergent" used as component (B1) is a metal-based detergent that contains calcium as the metal, and contains at least a calcium-based detergent (component (B1-1)) that contains boron and calcium. By including component (B1-1) in component (B1), it is possible to effectively reduce friction and improve LSPI suppression ability, compared to when component (B1-1) is not included.

The "calcium-based detergent" used as the (B1) component must contain the (B1-1) component containing boron and calcium, but may contain calcium-based detergents other than the (B1-1) component. As calcium-based detergents other than the (B1-1) component, known calcium-based detergents that do not contain boron (known metal-based detergents that do not contain boron and contain calcium as a metal) can be used as appropriate. In this way, the (B1) component can be made up of only the (B1-1) component; or a mixture of the (B1-1) component and a calcium-based detergent that does not contain boron; depending on the purpose, it is possible to use as appropriate.

The type of calcium-based detergent used as the component (B1) is not particularly limited, and examples include sulfonate detergents, phenate detergents, and salicylate detergents that contain calcium as a metal. Among these calcium-based detergents, salicylate detergents that contain calcium as a metal are preferred from the viewpoint of friction reduction performance.

There are no particular limitations on the sulfonate detergent containing calcium as the metal (calcium sulfonate detergent), and any known detergent can be used as appropriate. Suitable examples of such calcium sulfonate detergents include calcium salts of alkyl aromatic sulfonic acids obtained by sulfonating alkyl aromatic compounds having a molecular weight of 300 to 1500 (more preferably 400 to 1300). Examples of the alkyl aromatic sulfonic acids include petroleum sulfonic acids and synthetic sulfonic acids. Furthermore, any known petroleum sulfonic acid or synthetic sulfonic acid can be used as appropriate. Furthermore, any known calcium sulfonate detergent that can be used in lubricating oil compositions can be used as appropriate.

There are no particular limitations on the salicylate detergent containing calcium as the metal (calcium salicylate detergent), and any known detergent can be used as appropriate. Examples of such salicylate detergents include calcium salts of alkylsalicylic acids having 1 to 2 alkyl or alkenyl groups with 4 to 36 carbon atoms (more preferably 14 to 30) as a substituent, and mixtures thereof. In addition, any known calcium salicylate detergent that can be used in lubricating oil compositions can be used as appropriate.

The component (B1-1) (calcium-based detergent containing boron and calcium) contained in the component (B1) is preferably a calcium-based detergent containing calcium borate, more preferably a calcium-based detergent overbased with calcium borate, and particularly preferably a calcium salicylate detergent overbased with calcium borate (calcium borate salicylate), from the viewpoint of friction reduction performance especially under severe sliding conditions.

From the viewpoint of improving fuel economy performance according to application conditions, a mixture of the (B1-1) component and (B1-2) a calcium-based detergent containing calcium carbonate can be suitably used as the (B1) component. The (B1-2) component (calcium-based detergent containing calcium carbonate) is not particularly limited, but is more preferably a calcium-based detergent overbased with calcium carbonate, and is particularly preferably a calcium salicylate detergent overbased with calcium carbonate.

When the (B1) component is a mixture of the (B1-1) component and a calcium-based detergent other than the (B1-1) component (preferably the (B1-2) component), the content of the (B1-1) component in the (B1) component is not particularly limited, but it is preferable that the amount of the (B1-1) component is 30 to 100 mass% (more preferably 45 to 100 mass%, and even more preferably 67 to 100 mass%) relative to the total amount of the (B1) component. When the (B1-1) component content is equal to or greater than the lower limit, it is possible to further improve the friction reduction performance under particularly severe sliding conditions compared to when the content is less than the lower limit.

Regarding the component (B1-1) used as the component (B1), the boron content in the component (B1-1) is preferably 1.0 to 5.0 mass% (more preferably 1.3 to 4.5 mass%, and even more preferably 2.0 to 3.0 mass%) relative to the total amount of the component (B1-1). When the content of B in the component (B1-1) is equal to or greater than the lower limit, it is possible to further improve the friction reduction performance and LSPI suppression performance compared to when the content is less than the lower limit, and on the other hand, when the content is equal to or less than the upper limit, it is possible to improve the stability of the lubricating oil composition compared to when the content exceeds the upper limit.

The calcium-based detergent used as component (B1) preferably has a calcium (Ca) content of 2.0 to 11.5 mass% (more preferably 4.0 to 10.0 mass%, and even more preferably 5.7 to 7.2 mass%) for each calcium-based detergent contained in component (B1) (when component (B1) consists of one type, that one type). When the calcium (Ca) content of each calcium-based detergent is equal to or greater than the lower limit, it is possible to improve the reduction of friction loss under low temperature conditions compared to when it is less than the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve the stability of the lubricating oil composition compared to when it exceeds the upper limit.

The base number (TBN) of each calcium-based detergent used as component (B1) is not particularly limited, but is 50 to 500 mgKOH/g, more preferably 100 to 500 mgKOH/g, and particularly preferably 150 to 500 mgKOH/g for each calcium-based detergent. When the base number of each calcium-based detergent used as component (B1) is equal to or greater than the lower limit, it is possible to improve the acid neutralization performance compared to when it is less than the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve the solubility of each additive in the lubricating oil composition compared to when it exceeds the upper limit. In this specification, "base number (TBN)" means the base number measured by the perchloric acid method in accordance with JIS K2501.

Component (B1) must be used so that the calcium content (Ca _(B1) ) derived from component (B1) based on the total mass of the composition is in the range of 1650 ppm by mass to 2500 ppm by mass (more preferably 1650 ppm by mass to 2200 ppm by mass, even more preferably 1700 ppm by mass to 1900 ppm by mass, and particularly preferably 1750 ppm by mass to 1900 ppm by mass). When the calcium content (Ca _(B1) ) is equal to or more than the lower limit, it is possible to improve the cleanliness compared to when it is below the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve both the LSPI suppression ability and the fuel saving performance compared to when it exceeds the upper limit.

The content of boron derived from component (B1) (B _(B1) ) is preferably 50 ppm by mass or more and 1000 ppm by mass or less (more preferably 200 ppm by mass or more and 700 ppm by mass or less, even more preferably 400 ppm by mass or more and 700 ppm by mass or less, and particularly preferably 400 ppm by mass or more and 650 ppm by mass or less) based on the total mass of the composition (based on the total amount of the lubricating oil composition). When the boron content (B _(B1) ) is equal to or more than the lower limit, it is possible to further improve the friction reducing performance and LSPI suppression ability compared to when it is below the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to further improve the friction reducing performance compared to when it exceeds the upper limit.

The content of component (B1) is preferably 1.5 to 3.5 mass% (more preferably 2.0 to 3.2 mass%, and even more preferably 2.4 to 2.9 mass%) based on the total amount of the lubricating oil composition. When the content of component (B1) is equal to or greater than the lower limit, it is possible to improve the cleanliness compared to when it is below the lower limit, and on the other hand, when the content is equal to or less than the upper limit, it is possible to further improve the friction reduction performance compared to when it exceeds the upper limit.

Furthermore, the content of boron derived from component (B1) (B _(B1) ) is preferably 50 mass% or more, more preferably 60 mass% to 100 mass%, and particularly preferably 70 mass% to 100 mass%, relative to the total amount of boron contained in the composition. When the ratio of B _(B1) to the total amount of boron in the composition is equal to or more than the above-mentioned lower limit, it is possible to further improve the LSPI suppression ability compared to when it is less than the above-mentioned lower limit.

Furthermore, the content of calcium derived from component (B1) (Ca _(B1) ) is preferably 50% by mass or more, more preferably 75% to 100% by mass, and particularly preferably 90% to 100% by mass, based on the total amount of calcium contained in the composition. When the proportion of Ca _(B1) to the total amount of calcium in the composition is equal to or more than the aforementioned lower limit, it is possible to further improve the LSPI inhibitory ability compared to when it is less than the aforementioned lower limit.

The boron content (B _(B1) ) derived from component (B1) based on the total mass of the composition, and the calcium content (Ca _(B1) ) derived from component (B1) based on the total mass of the composition, can be measured by the measurement method specified in JPI-5S-38.

Regarding component (B2)
The "magnesium-based detergent" used as the component (B2) is not particularly limited, and any known metal-based detergent containing magnesium as a metal can be appropriately used. Examples of such magnesium-based detergents include sulfonate detergents, phenate detergents, and salicylate detergents containing magnesium as a metal. Among such magnesium-based detergents, sulfonate detergents containing magnesium as a metal and salicylate detergents containing magnesium as a metal are preferred from the viewpoint of friction reduction performance.

There are no particular limitations on the sulfonate detergent containing magnesium as the metal (magnesium sulfonate detergent), and known detergents can be used as appropriate. Suitable examples of such magnesium sulfonate detergents include magnesium salts of alkyl aromatic sulfonic acids obtained by sulfonating an alkyl aromatic compound having a molecular weight of 300 to 1500 (more preferably 400 to 1300). Examples of the alkyl aromatic sulfonic acids include petroleum sulfonic acids and synthetic sulfonic acids. Furthermore, known petroleum sulfonic acids and synthetic sulfonic acids can be used as appropriate. Furthermore, known magnesium sulfonate detergents that can be used in lubricating oil compositions can be used as appropriate.

There are no particular limitations on the salicylate detergent containing magnesium as the metal (magnesium salicylate detergent), and any known detergent can be used as appropriate. Examples of such salicylate detergents include magnesium salts of alkylsalicylic acids having 1 to 2 alkyl or alkenyl groups with 4 to 36 carbon atoms (more preferably 14 to 30) as a substituent, and mixtures thereof. In addition, any known magnesium salicylate detergent that can be used in lubricating oil compositions can be used as appropriate.

The magnesium-based detergent is preferably a magnesium-based detergent containing magnesium carbonate. The magnesium-based detergent containing magnesium carbonate is not particularly limited, but is more preferably a magnesium-based detergent overbased with magnesium carbonate, and among them, from the viewpoint of suppressing the loss of base number when moisture is mixed in (the loss of base number due to the coarsening of the magnesium-based detergent under water-added conditions, and the settling or precipitation), it is particularly preferable to use a magnesium sulfonate detergent overbased with magnesium carbonate.

The magnesium (Mg) content in component (B2) is preferably 6.0 to 10.0 mass% (more preferably 7.5 to 9.5 mass%, and even more preferably 7.5 to 9.1 mass%) of the total amount of component (B2). When the magnesium content in component (B2) is equal to or greater than the lower limit, it is possible to reduce viscous resistance compared to when it is below the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve the stability of the lubricating oil composition compared to when it exceeds the upper limit.

The base number (TBN) of each magnesium-based detergent used as component (B2) is not particularly limited, but is preferably 50 to 500 mgKOH/g, more preferably 100 to 500 mgKOH/g, and particularly preferably 150 to 500 mgKOH/g. When the base number of component (B2) is equal to or greater than the lower limit, it is possible to further improve the reduction in viscous resistance compared to when it is below the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve the stability of the lubricating oil composition compared to when it exceeds the upper limit.

The (B2) component must be used so that the content of magnesium (Mg _(B2) ) derived from the (B2) component based on the total mass of the composition is in the range of 20 ppm by mass to 400 ppm by mass (more preferably 20 ppm by mass to 300 ppm by mass, even more preferably 100 ppm by mass to 300 ppm by mass, and particularly preferably 100 ppm by mass to 200 ppm by mass). When the magnesium content (Mg _(B2) ) is equal to or more than the lower limit, it is possible to improve the LSPI suppression ability compared to when it is below the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve the fuel saving performance compared to when it exceeds the upper limit. The content of magnesium (Mg _(B2) ) derived from the (B2) component based on the total mass of the composition can be measured by the measurement method described in JPI-5S-38.

The content of component (B2) is preferably 0.01 to 0.60 mass% (more preferably 0.01 to 0.40 mass%, and even more preferably 0.10 to 0.27 mass%) based on the total amount of the lubricating oil composition. When the content of component (B2) is equal to or greater than the lower limit, it is possible to improve the acid neutralization performance compared to when it is less than the lower limit, and on the other hand, when the content is equal to or less than the upper limit, it is possible to further improve the friction reduction performance compared to when it exceeds the upper limit.

Furthermore, the content of magnesium derived from component (B2) (Mg _(B2) ) is preferably 50% by mass or more, more preferably 75% to 100% by mass, and particularly preferably 90% to 100% by mass, relative to the total amount of magnesium contained in the composition. When the proportion of Mg _(B2) relative to the total amount of magnesium in the composition is at least the above lower limit, it is possible to further improve fuel economy performance compared to when it is less than the above lower limit.

Component (B) may contain other metal-based detergents other than components (B1) and (B2) as necessary. The ratio of the total amount of components (B1) and (B2) to the total amount of component (B) is preferably 50 to 100 mass% (more preferably 75 to 100 mass%, particularly preferably 90 to 100 mass%). When the ratio of the total amount of components (B1) and (B2) is equal to or greater than the lower limit, the LSPI suppression ability and friction reduction performance can be further improved compared to when the ratio is less than the lower limit. There are no particular restrictions on the other metal-based detergents other than components (B1) and (B2), and known metal-based detergents can be used as appropriate. From the viewpoint of achieving both LSPI suppression ability and friction reduction performance, it is more preferable to use a mixture of components (B1) and (B2) as component (B).

The content of component (B) is preferably 1.0 to 4.0 mass% (more preferably 2.2 to 3.0 mass%, and even more preferably 2.6 to 3.0 mass%) based on the total amount of the lubricating oil composition. When the content of component (B) is equal to or greater than the lower limit, it is possible to improve the acid neutralization performance compared to when it is less than the lower limit, and on the other hand, when the content is equal to or less than the upper limit, it is possible to further improve the friction reduction performance compared to when it exceeds the upper limit.

In addition, in the lubricating oil composition for internal combustion engines of the present invention, when the content (mass ratio) of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , and the content (mass ratio) of calcium in component (B1) based on the total mass of the composition is represented as Ca _(B1) , the ratio of B(B1 _{) to Ca(B1)} (B _{(B1) /} Ca _(B1) ) is 0.15 or more and 0.35 or less (more preferably 0.21 or more and 0.30 or less, particularly preferably 0.26 or more and 0.29 or less). When B _(B1) /Ca _(B1) is equal to or greater than the lower limit, the LSPI suppression ability can be made superior compared to when it is below the lower limit, and as a result, it is possible to achieve both excellent LSPI suppression ability and excellent fuel saving performance. On the other hand, when it is equal to or less than the upper limit, the friction coefficient can be made lower compared to when it exceeds the upper limit, and therefore it is possible to achieve both excellent LSPI suppression ability and excellent fuel saving performance.

In the lubricating oil composition for internal combustion engines of the present invention, when the content (mass ratio) of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , the content (mass ratio) of calcium in component (B1) based on the total mass of the composition is represented as Ca _(B1) , and the content (mass ratio) of magnesium in component (B2) based on the total mass of the composition is represented as Mg _(B2) , the ratio of B(B1) to the total amount of Ca _(B1) and Mg _(B2) (Ca _(B1) +Mg _(B2) ), (B _{(B1 )} /[Ca _(B1) +Mg _(B2) ]), is 0.13 or more and 0.29 or less (more preferably 0.23 or more and 0.29 or less, particularly preferably 0.25 or more and 0.29 or less). When B _(B1) /[Ca _(B1) +Mg _(B2) ] is equal to or greater than the lower limit, it is possible to improve the LSPI suppression ability compared to when it is below the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to improve the fuel economy performance compared to when it exceeds the upper limit.

In the lubricating oil composition for internal combustion engines of the present invention, when the content (mass ratio) of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , and the total amount of calcium in the composition based on the total mass of the composition (total calcium content: mass ratio) is represented as Ca, it is preferable that the ratio of B _(B1) to Ca (B _(B1) /Ca) is 0.15 or more and 0.35 or less (more preferably 0.21 or more and 0.31 or less, particularly preferably 0.26 or more and 0.30 or less). When _B(B1) /Ca is equal to or more than the lower limit, it is possible to further improve the LSPI suppression ability compared to when it is less than the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to further improve the fuel saving performance compared to when it exceeds the upper limit.

In the lubricating oil composition for internal combustion engines of the present invention, when the content (mass ratio) of boron in the (B1) component based on the total mass of the composition is represented as B _(B1) , the total amount of calcium in the composition based on the total mass of the composition (total calcium content: mass ratio) is represented as Ca, and the total amount of magnesium in the composition based on the total mass of the composition (total magnesium content: mass ratio) is represented as Mg, it is preferable that the ratio of B _(B1) to the total amount of Ca and Mg (Ca+Mg) (B _(B1) /[Ca+Mg]) is 0.13 or more and 0.29 or less (more preferably 0.23 or more and 0.29 or less, particularly preferably 0.25 or more and 0.29 or less). When B _(B1) /[Ca+Mg] is equal to or more than the lower limit, it is possible to further improve the LSPI suppression ability compared to when it is less than the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to further improve the fuel saving performance compared to when it exceeds the upper limit.

There are no particular limitations on the method for preparing the metal-based detergent used as component (B), and any known method can be used as appropriate.

In addition to the components (A) and (B) (components consisting of components (B1) and (B2)), the lubricating oil composition for internal combustion engines of the present invention may contain, depending on the purpose, appropriate known additives that are generally used in lubricating oil compositions for internal combustion engines in order to further improve its performance. Components that can be suitably used as such additives are described below.

<Component (C): Poly(meth)acrylate-based viscosity index improver>
The lubricating oil composition for internal combustion engines of the present invention preferably contains (C) a poly(meth)acrylate-based viscosity index improver, since it is possible to further improve fuel economy performance. Here, as the "poly(meth)acrylate-based viscosity index improver", known poly(meth)acrylate-based compounds used as viscosity index improvers (for example, "viscosity index improver" described in WO 2019/221295, "poly(meth)acrylate compound" described in JP 2018-177986 A, "comb polymer" described in JP 2017-101211 A, "viscosity index improver" described in WO 2016/159006 A, "viscosity index improver" described in WO 2017/099052 A, "viscosity index improver" described in JP 2017-110196 A, "(co)polymer (A)" described in JP 2017-110196 A, etc.) can be appropriately used.

The poly(meth)acrylate polymer used as component (C) is not particularly limited in structure, and may be either a so-called linear poly(meth)acrylate polymer or a so-called comb-type poly(meth)acrylate polymer. Among these, from the viewpoint of improving fuel efficiency performance associated with improved viscosity-temperature characteristics and oil film formability, it is more preferable for component (C) to contain a comb-type poly(meth)acrylate polymer. Furthermore, it is particularly preferable for the poly(meth)acrylate viscosity index improver to be a comb-type poly(meth)acrylate polymer. As such a comb-shaped poly(meth)acrylate polymer, a known poly(meth)acrylate polymer having a so-called comb-shaped structure (for example, the "comb polymer" described in JP 2017-101211 A, the "comb poly(meth)acrylate" described in JP 2018-177986 A, the "comb poly(meth)acrylate" described in WO 2016/159006 A, the "viscosity index improver" described in JP 2017-110196 A, the "(co)polymer (A)" described in JP 2017-110196 A, etc.) can be appropriately used.

As such a comb-shaped poly(meth)acrylate polymer, a poly(meth)acrylate polymer having a comb-shaped structure, which is a copolymer of (meth)acrylate and a (meth)acrylate macromonomer, can be appropriately used. In addition, such a comb-shaped poly(meth)acrylate polymer may be a copolymer of (meth)acrylate, a (meth)acrylate macromonomer, and other monomers (e.g., ethylene, styrene, 1-butene, etc.). In this specification, "(meth)acrylate" means acrylate and/or methacrylate.

Among the comb-shaped poly(meth)acrylate polymers, those represented by the following formula (1):

[In formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents a linear or branched hydrocarbon group having 2 to 10 carbon atoms.]
(hereinafter, sometimes simply referred to as “monomer (M-1)”) and a (meth)acrylate represented by the following formula (2):

[In formula (2), ^R3 represents a hydrogen atom or a methyl group, and ^R4 represents a hydrocarbon group having 12 to 24 carbon atoms.]
As a suitable example, there can be mentioned a copolymer of a (meth)acrylate macromonomer represented by the following formula (hereinafter, sometimes simply referred to as "macromonomer (M-2)"):

In formula (1), ^R2 is a linear or branched hydrocarbon group (more preferably an alkyl group) having from 2 to 10 carbon atoms. The number of carbon atoms of the hydrocarbon group selected as ^R2 is preferably from 4 to 10 (more preferably from 4 to 8, particularly preferably from 4 to 6).

The number of carbon atoms of the hydrocarbon group selected as R ⁴ in formula (2) is 12 to 24 (more preferably 12 to 20, particularly preferably 12 to 18). When the number of carbon atoms is equal to or more than the lower limit, a high viscosity index can be achieved, and when the number of carbon atoms is equal to or less than the upper limit, good flow is possible under low temperature conditions. The hydrocarbon group may be linear or branched. Furthermore, as the macromonomer (M-2), for example, a macromonomer derived from a hydrogenated polyolefin obtained by copolymerizing butadiene and isoprene may be used. As such a macromonomer (M-2), for example, a known macromonomer (for example, a macromonomer described in JP-A-2018-177986 or "monomer (a)" described in JP-A-2017-110196) may be appropriately used.

In addition, in the copolymer of monomer (M-1) and macromonomer (M-2), the copolymerization molar ratio of these monomers is not particularly limited, but it is preferable that monomer (M-1):monomer (M-2) is about 20:80 to 90:10 (more preferably 30:70 to 80:20, and even more preferably 40:60 to 70:30).

The weight average molecular weight (Mw) of the poly(meth)acrylate polymer (preferably a comb-type poly(meth)acrylate polymer) contained in the poly(meth)acrylate viscosity index improver is preferably 100,000 to 1,000,000 (more preferably 300,000 to 1,000,000, and even more preferably 600,000 to 800,000). When the weight average molecular weight is equal to or greater than the lower limit, the viscosity index when dissolved in a lubricating base oil is improved compared to when the weight average molecular weight is less than the lower limit, and the fuel saving performance and low-temperature viscosity characteristics are further improved. On the other hand, when the weight average molecular weight is equal to or less than the upper limit, the fuel saving performance and low-temperature viscosity characteristics are further improved compared to when the weight average molecular weight exceeds the upper limit, and it is possible to improve the shear stability, solubility in lubricating base oil, and storage stability.

In addition, when the (C) poly(meth)acrylate-based viscosity index improver contains a comb-type poly(meth)acrylate-based polymer, the content of the comb-type poly(meth)acrylate-based polymer relative to the total amount of the (C) component is preferably 30% by mass or more (more preferably 50 to 100% by mass, even more preferably 95 to 100% by mass, and particularly preferably 98 to 100% by mass). When the content of the comb-type poly(meth)acrylate-based polymer in the (C) component is equal to or more than the lower limit, it is possible to further improve fuel efficiency performance by improving the viscosity-temperature characteristics and oil film formability, compared to when the content is less than the lower limit. Note that, from the viewpoint of improving the viscosity-temperature characteristics and oil film formability, it is more preferable to use a component (C) consisting only of a comb-type poly(meth)acrylate-based polymer.

The content of component (C) is preferably 5 to 15 mass % (more preferably 7 to 11 mass %, and even more preferably 9 to 11 mass %) based on the total amount of the lubricating oil composition. When the content of component (C) is equal to or greater than the lower limit, it is possible to improve the viscosity-temperature characteristics and improve the anti-wear properties by forming an oil film compared to when the content is less than the lower limit, and on the other hand, when the content is equal to or less than the upper limit, it is possible to further improve the fuel saving performance by suppressing excessive thickening compared to when the content exceeds the upper limit.

The method for preparing the poly(meth)acrylate polymer used in component (C) is not particularly limited, and known methods can be used as appropriate. For example, a method for obtaining a poly(meth)acrylate polymer by radical solution polymerization of monomer (M-1), macromonomer (M-2), and, if necessary, other monomers in the presence of a polymerization initiator (e.g., benzoyl peroxide, etc.) may be used as such a preparation method.

<Component (D): Ashless Dispersant>
The lubricating oil composition for internal combustion engines of the present invention can highly disperse metal powder generated by wear during use, and can improve anti-wear properties and oxidation stability, so it is preferable to further contain an ashless dispersant (D). As the component (D), known compounds used as ashless dispersants in the field of lubricating oil compositions (for example, the "nitrogen-containing ashless dispersant" described in WO 2019/221295, as well as ashless dispersants described in JP 2003-155492 A, JP 2020-76004 A, WO 2013/147162, etc.) can be suitably used.

Examples of the ashless dispersant include mono- or bis-succinimides having at least one linear or branched alkyl or alkenyl group in the molecule, benzylamines having at least one alkyl or alkenyl group in the molecule, or polyamines having at least one alkyl or alkenyl group in the molecule, or products modified with boron compounds, carboxylic acids, phosphoric acids, or the like. In the (D) component, the linear or branched alkyl or alkenyl group is preferably a linear or branched alkyl or alkenyl group having 40 to 400 carbon atoms (more preferably 60 to 350).

As component (D), from the viewpoint of providing better dispersibility for metal powders and the like, (D1) boronated succinimide (such as the boron-modified mono- or bis-succinimide compounds described above), (D2) non-boronated succinimide (such as the mono- or bis-succinimide compounds described above), and mixtures thereof can be preferably used.

As the (D1) component and the (D2) component, known boronized succinimide compounds and non-boronized succinimide compounds used as ashless dispersants can be appropriately used. As the (D1) component and the (D2) component, the nitrogen atom content is preferably 0.5 to 3.0 mass% based on the total amount of the component ((D1) component or (D2) component). As the (D1) component, the boron content is preferably 0.1 to 5.0 mass% (more preferably 0.1 to 3.0 mass%) based on the total amount of the (D1) component. Furthermore, as the (D1) component and the (D2) component, the weight average molecular weight is preferably 1000 to 20000 (more preferably 2000 to 20000, and even more preferably 4000 to 15000). As the (D) component, one type may be used alone, or two or more types may be used in combination.

When the lubricating oil composition of the present invention contains component (D), the content of component (D) is not particularly limited, but is preferably 0.1 to 5.0 mass% (more preferably 1.0 to 2.5 mass%) based on the total amount of the lubricating oil composition. By keeping the content of component (D) within the above range, it is possible to improve the dispersion performance when insoluble matter is generated.

Furthermore, when component (D) contains component (D1), the content of boron derived from component (D1) (B _(D1) ) is preferably 90 mass% or less (more preferably 70 mass% or less, and even more preferably 27 mass% or less) relative to the total amount of boron contained in the composition. When the ratio of B _(D1) to the total amount of boron in the composition is equal to or less than the upper limit, it is possible to suppress excessive ash generation compared to when the ratio exceeds the upper limit.

<Component (E): Antioxidant>
The lubricating oil composition of the present invention preferably further contains an antioxidant (E) since this makes it possible to improve the oxidation stability. The component (E) is not particularly limited, and any known antioxidant used in the field of lubricating oil compositions can be appropriately used, such as (E1) a phenol-based antioxidant, (E2) an amine-based antioxidant, (E3) a metal-based antioxidant (copper-based antioxidant, molybdenum-based antioxidant, etc.), etc.

As the (E1) component, known compounds can be used as appropriate, such as 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters; methyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate and other hindered phenol compounds and bisphenol compounds.

As the (E2) component, for example, compounds known as amine-based antioxidants such as aromatic amine-based antioxidants and hindered amine-based antioxidants (for example, compounds exemplified in WO 2020/095970) can be appropriately used. As the aromatic amine-based antioxidant, alkylated diphenylamine and alkylated phenyl-α-naphthylamine can be preferably used. As the hindered amine-based antioxidant, for example, a compound having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivative) can be preferably used. As the amine-based antioxidant, aromatic amine-based antioxidants can be more preferably used.

Examples of the (E3) component include organic molybdenum-based antioxidants such as oxymolybdenum sulfide or an alkylamine complex of oxymolybdenum, oxymolybdenum sulfide or an alkenyl succinimide complex of oxymolybdenum, oxymolybdenum sulfide dithiocarbamate, and oxymolybdenum sulfide dithiophosphate. Among these molybdenum-based antioxidants, oxymolybdenum sulfide or an oxymolybdenum-ditridecylamine complex, and oxymolybdenum sulfide or an oxymolybdenum-alkenyl succinimide complex are more preferred, as they suppress viscosity increase and make it easier to maintain fuel-saving performance over the long term, and they also have superior high-temperature detergency.

The (E) component may be used alone or in combination of two or more. As the (E) component, the (E1), (E2) and (E3) components may be used in appropriate combination. Among them, it is preferable to use the (E2) component in combination with the (E3) component, since this makes it possible to suppress oxidative deterioration of the lubricating oil composition for a long period of time.

When the lubricating oil composition for internal combustion engines of the present invention contains component (E), the content of component (E) is preferably 1.5 mass% or more and 2.5 mass% or less (more preferably 1.7 mass% or more and 2.0 mass% or less) based on the total amount of the lubricating oil composition. By setting the content of component (E) within the above range, it is possible to improve the deterioration inhibition properties of the lubricating oil composition while maintaining the solubility of component (E).

When the lubricating oil composition for internal combustion engines of the present invention contains the component (E1), the content of the component (E1) is preferably 2.0 mass% or less (more preferably 0.5 mass% or less) based on the total amount of the lubricating oil composition. By keeping the content of the component (E1) within the above range, it is possible to improve the deterioration suppression properties of the lubricating oil composition while maintaining the solubility of the components.

When the lubricating oil composition for internal combustion engines of the present invention contains the component (E2), the content of the component (E2) is preferably 1.3 mass% or more and 2.3 mass% or less (more preferably 1.5 mass% or more and 1.9 mass% or less) based on the total amount of the lubricating oil composition. By setting the content of the component (E2) within the above range, it is possible to improve the deterioration inhibition properties of the lubricating oil composition while maintaining the solubility of the components.

Furthermore, when the lubricating oil composition for internal combustion engines of the present invention contains the component (E3), the content of the component (E3) is preferably 0.3 mass% or less (more preferably 0.1 mass% or more and 0.2 mass% or less) based on the total amount of the lubricating oil composition. By keeping the content of the component (E3) within the above range, it becomes possible to improve the deterioration inhibition properties of the lubricating oil composition while maintaining the solubility of the component.

<(F) Molybdenum-based friction modifier>
The lubricating oil composition for internal combustion engines of the present invention preferably contains (F) a molybdenum-based friction modifier (oil-soluble organic molybdenum compound). As such a molybdenum-based friction modifier, any of those known in the art that are used as molybdenum-based friction modifiers in the field of lubricating oil compositions can be appropriately used.

Molybdenum dithiocarbamate (sulfurized molybdenum dithiocarbamate or sulfurized oxymolybdenum dithiocarbamate) is more preferable as component (F) from the viewpoint of reducing friction under boundary lubrication conditions. Examples of the molybdenum dithiocarbamate (MoDTC) include compounds represented by the following general formula (3):

[In formula (3), R ¹⁰ to R ¹³ each independently represent an alkyl group having 2 to 24 carbon atoms or an (alkyl)aryl group having 6 to 24 carbon atoms;
Y ¹ to Y ⁴ each independently represent a sulfur atom or an oxygen atom, and at least one of Y ¹ to Y ⁴ represents a sulfur atom.]
Compounds represented by the following formula (I) can be preferably used.

R ¹⁰ to R ¹³ in the general formula (3) may be the same or different, and each represents an alkyl group having 2 to 24 carbon atoms or an (alkyl)aryl group having 6 to 24 carbon atoms (preferably an alkyl group having 4 to 13 carbon atoms or an (alkyl)aryl group having 10 to 15 carbon atoms). The alkyl group that can be selected as R ¹⁰ to R ¹³ may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, and may be linear or branched. In addition, the "(alkyl)aryl group" referred to here means an "aryl group or an alkylaryl group". In the alkylaryl group, the substitution position of the alkyl group in the aromatic ring is arbitrary. In addition, Y ¹ to Y ⁴ in the general formula (3) are each independently a sulfur atom or an oxygen atom, and at least one of Y ¹ to Y ⁴ is a sulfur atom.

Examples of the oil-soluble organic molybdenum compounds other than the molybdenum dithiocarbamate include molybdenum dithiophosphate; molybdenum compounds (e.g., molybdenum oxides such as molybdenum dioxide and molybdenum trioxide; molybdic acids such as orthomolybdic acid, paramolybdic acid, and (poly)molybdic sulfide; metal salts of these molybdic acids; molybdates such as ammonium salts; molybdenum sulfides such as molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, and polymolybdenum sulfide; molybdic acid; metal salts or amine salts of molybdic sulfide; and molybdenum chloride. and molybdenum halides.) and a sulfur-containing organic compound (e.g., alkyl(thio)xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetrahydrocarbyl thiuram disulfide, bis(di(thio)hydrocarbyl dithiophosphonate) disulfide, organic (poly)sulfide, sulfurized ester, etc.) or a complex of other organic compounds; and sulfur-containing organic molybdenum compounds such as the molybdenum sulfide and molybdic acid sulfide and alkenyl succinimide complexes. The organic molybdenum compound may be a mononuclear molybdenum compound or a polynuclear molybdenum compound such as a dinuclear molybdenum compound or a trinuclear molybdenum compound.

As an oil-soluble organomolybdenum compound other than the molybdenum dithiocarbamate, it is also possible to use an organomolybdenum compound that does not contain sulfur. Examples of organomolybdenum compounds that do not contain sulfur include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols. Among these, molybdenum-amine complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols are preferred.

The content of component (F) in the lubricating oil composition is preferably an amount such that the molybdenum content is 100 to 2000 ppm by mass (more preferably 300 to 1500 ppm by mass, even more preferably 500 to 1200 ppm by mass, and particularly preferably 700 to 1000 ppm by mass) based on the total amount of the lubricating oil composition. By having the content of component (F) equal to or greater than the lower limit, it is possible to further improve fuel economy performance and LSPI suppression ability. In addition, by having the content of component (F) equal to or less than the upper limit, it is possible to improve the storage stability of the lubricating oil composition.

<(G) Antiwear Agent>
The lubricating oil composition for internal combustion engines of the present invention preferably contains (G) an antiwear agent. The antiwear agent is not particularly limited, and known compounds used as antiwear agents in lubricating oil compositions can be used. As the antiwear agent, for example, sulfur-based, phosphorus-based, and sulfur-phosphorus-based antiwear agents can be used. Specifically, the antiwear agent includes phosphites, thiophosphites, dithiophosphites, trithiophosphites, phosphates, thiophosphates, dithiophosphates, trithiophosphates, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamates, zinc dithiocarbamates, disulfides, polysulfides, sulfurized olefins, and sulfurized oils and fats.

Among these anti-wear agents, phosphorus-based anti-wear agents are preferred, and zinc-containing phosphorus-based anti-wear agents are more preferred, and among these, those represented by the following formula (4):

[In formula (4), R ¹⁴ to R ¹⁷ each independently represent a linear or branched alkyl group having 1 to 24 carbon atoms.]
Zinc dialkyldithiophosphate (ZnDTP) represented by the following formula is particularly preferred.

R ¹⁴ to R ¹⁷ in the general formula (4) each independently represent a linear or branched alkyl group having 1 to 24 carbon atoms, and may be a combination of different groups. The number of carbon atoms in R ¹⁴ to R ¹⁷ is preferably 3 or more, more preferably 12 or less, and more preferably 8 or less. R ¹⁴ to R ¹⁷ may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, but is preferably a primary alkyl group, a secondary alkyl group, or a combination thereof, and further, the molar ratio of the primary alkyl group to the secondary alkyl group (primary alkyl group:secondary alkyl group) is preferably 0:100 to 30:70. This ratio may be a combination ratio of alkyl chains in the molecule, or may be a mixture ratio of ZnDTP having only a primary alkyl group and ZnDTP having only a secondary alkyl group. By being dominated by secondary alkyl groups, it is possible to further improve fuel saving performance. In addition, the method for producing ZnDTP is not particularly limited, and any known method can be appropriately used. For example, a method may be employed in which an alcohol having an alkyl group corresponding to R ¹⁴ to R ¹⁷ is reacted with diphosphorus pentasulfide to synthesize a dithiophosphoric acid, and the dithiophosphoric acid is then neutralized with zinc oxide.

The content of the anti-wear agent is preferably 0.1 to 5.0 mass % or less (more preferably 0.5 to 3.0 mass % or less) based on the total amount of the lubricating oil composition. If the content of the anti-wear agent is within the above numerical range, a sufficient anti-wear effect can be obtained.

<(H) Pour Point Depressant>
The lubricating oil composition for internal combustion engines of the present invention preferably contains a pour point depressant (H). There are no particular limitations on the pour point depressant, and any known pour point depressant used in lubricating oil compositions can be used as appropriate. Examples of such pour point depressants include poly(meth)acrylates, ethylene-vinyl acetate copolymers, and the like, and among these, polymethacrylates are preferred. In addition, the poly(meth)acrylates (more preferably polymethacrylates) used as pour point depressants preferably have a weight average molecular weight of 20,000 to 100,000 (more preferably 20,000 to 80,000) from the viewpoints of pour point depressing action and shear stability.

The pour point depressant may be used alone or in combination of two or more. When a pour point depressant is used, its content is preferably 0.01 to 1.0 mass % (more preferably 0.03 to 0.6 mass %) based on the total amount of the lubricating oil composition.

<(I) Other Components>
The lubricating oil composition for internal combustion engines of the present invention may further contain other additives that can be used in the lubricating oil composition in addition to the above-mentioned components. Such other components are not particularly limited, but examples thereof include antifoaming agents, rust inhibitors, antiemulsifiers, metal deactivators, etc. Such other components can be appropriately used, and examples of such other components include silicone oils having a kinetic viscosity of 1,000 to 100,000 mm ² /s at 25° C., alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long-chain fatty acids, methyl salicylate, and o-hydroxybenzyl alcohol. The content of such other components may be appropriately designed for each component so as to be an optimal amount depending on the application, and is not particularly limited, but it is preferable that the content of each component is about 0.001 to 5 mass% based on the total amount of the lubricating oil composition. The content of each component utilized as component (I) is preferably 0.001 to 0.05 parts by mass, relative to 100 parts by mass of the total mass of the components in the lubricating oil composition other than that component.

[Lubricating Oil Composition]
In the lubricating oil composition for internal combustion engines of the present invention, the boron content based on the total mass of the composition (boron content based on the total amount of the lubricating oil composition) is 1000 ppm by mass or less (more preferably 200 ppm by mass to 700 ppm by mass, and even more preferably 400 ppm by mass to 650 ppm by mass). By setting the boron content based on the total amount of the composition to the above upper limit or less, it is possible to improve the friction reducing performance compared to when the boron content exceeds the above upper limit, while when the boron content is equal to or greater than the above lower limit, it is possible to improve the LSPI suppression ability compared to when the boron content is less than the above lower limit.

In the lubricating oil composition for internal combustion engines of the present invention, the calcium content based on the total amount of the lubricating oil composition is preferably 1650 ppm by mass or more and 2500 ppm by mass or less (more preferably 1700 ppm by mass or more and 1900 ppm by mass or less, and even more preferably 1750 ppm by mass or more and 1900 ppm by mass or less). By setting the calcium content based on the total amount of the composition to the upper limit or less, it is possible to achieve both LSPI suppression ability and friction reduction performance compared to when the calcium content exceeds the upper limit, and on the other hand, when the calcium content is equal to or more than the lower limit, it is possible to improve detergency by improving acid neutralization compared to when the calcium content is less than the lower limit.

In the lubricating oil composition for internal combustion engines of the present invention, the magnesium content based on the total amount of the lubricating oil composition is preferably 20 ppm by mass or more and 400 ppm by mass or less (more preferably 20 ppm by mass or more and 300 ppm by mass or less, and even more preferably 100 ppm by mass or more and 200 ppm by mass or less). By setting the magnesium content based on the total amount of the composition to the upper limit or less, it is possible to improve the friction reduction performance compared to when the magnesium content exceeds the upper limit, and on the other hand, when the magnesium content is equal to or more than the lower limit, it is possible to improve the acid neutralization performance compared to when the magnesium content is less than the lower limit.

In the lubricating oil composition for internal combustion engines of the present invention, when the composition contains molybdenum, the molybdenum content based on the total amount of the lubricating oil composition is preferably 100 ppm by mass or more and 1200 ppm by mass or less (more preferably 700 ppm by mass or more and 1000 ppm by mass or less). By setting the molybdenum content based on the total amount of the composition within the above range, it is possible to further improve the friction reduction performance while maintaining the solubility of the additives in the composition.

In the lubricating oil composition for internal combustion engines of the present invention, when phosphorus is contained in the composition, the phosphorus content based on the total amount of the lubricating oil composition is preferably 600 ppm by mass or more and 800 ppm by mass or less (more preferably 700 ppm by mass or more and 800 ppm by mass or less). By setting the phosphorus content based on the total amount of the composition within the above range, excessive catalyst poisoning can be avoided while simultaneously achieving both friction reduction performance and wear prevention performance.

In the lubricating oil composition for internal combustion engines of the present invention, when sulfur is contained in the composition, the sulfur content based on the total amount of the lubricating oil composition is preferably 500 ppm by mass or more and 3000 ppm by mass or less (more preferably 1000 ppm by mass or more and 2700 ppm by mass or less). By setting the sulfur content based on the total amount of the composition within the above range, it is possible to improve seizure resistance.

In the lubricating oil composition for internal combustion engines of the present invention, when zinc is contained in the composition, the zinc content based on the total amount of the lubricating oil composition is preferably 500 ppm by mass or more and 1,300 ppm by mass or less (more preferably 700 ppm by mass or more and 900 ppm by mass or less). By setting the zinc content based on the total amount of the composition within the above range, it is possible to improve the anti-wear properties.

The contents of boron, calcium, magnesium, molybdenum, zinc, sulfur and phosphorus in the lubricating oil composition can each be measured in accordance with JPI-5S-62.

In the lubricating oil composition for internal combustion engines of the present invention, the ratio of the boron content based on the total amount of the lubricating oil composition to the calcium content based on the total amount of the lubricating oil composition (mass ratio: [boron]/[calcium]) is preferably 0.15 to 0.35 (more preferably 0.25 to 0.35, and even more preferably 0.26 to 0.30). By keeping such a mass ratio within the above range, it is possible to improve the LSPI suppression ability while maintaining the friction reduction performance.

In addition, in the lubricating oil composition for internal combustion engines of the present invention, the ratio of the boron content based on the total amount of the lubricating oil composition to the total amount (total amount) of calcium based on the total amount of the lubricating oil composition and magnesium based on the total amount of the lubricating oil composition [mass ratio: [boron]/([calcium]+[magnesium])] is preferably 0.13 to 0.29 (more preferably 0.20 to 0.29, and even more preferably 0.25 to 0.28). By setting such a mass ratio within the above range, it is possible to improve the LSPI suppression ability while maintaining the friction reduction performance.

The lubricating oil composition for internal combustion engines of the present invention preferably has a kinetic viscosity at 100°C of 4.0 to 9.3 mm ² /s (more preferably 6.5 to 8.0 mm ² /s). The lubricating oil composition of the present invention preferably has a kinetic viscosity at 40°C of 23.0 to 40.0 ^{mm 2} /s (more preferably 26.0 to 30.0 mm ² /s). When these kinetic viscosities are equal to or less than the upper limit, it becomes possible to further improve fuel saving performance compared to when the kinetic viscosities exceed the upper limit. On the other hand, when these kinetic viscosities are equal to or more than the lower limit, it becomes possible to improve wear prevention due to oil film retention compared to when the kinetic viscosities are less than the lower limit.

The lubricating oil composition for internal combustion engines of the present invention preferably has a viscosity index of 180 or more (more preferably 200 or more, even more preferably 220 or more, and particularly preferably 225 or more). When the viscosity index is equal to or greater than the lower limit, it is possible to improve the viscosity-temperature characteristics and anti-wear properties of the lubricating oil composition and further improve the fuel economy performance, compared to when the viscosity index is less than the lower limit. In addition, when the viscosity index is equal to or greater than the lower limit, it is possible to reduce the evaporation loss of the lubricating oil, and it is possible to reduce the consumption of the lubricating oil.

The HTHS viscosity of the lubricating oil composition for internal combustion engines of the present invention at 150°C is preferably 1.7 mPa·s or more and 2.9 mPa·s or less (more preferably 2.3 mPa·s or more and 2.8 mPa·s or less, even more preferably 2.6 mPa·s or more and 2.8 mPa·s or less, and particularly preferably 2.6 mPa·s). When the HTHS viscosity at 150°C is equal to or more than the lower limit, it is possible to improve the wear resistance under high shear conditions compared to when it is less than the lower limit, and on the other hand, when it is equal to or less than the upper limit, it is possible to further improve the fuel saving performance by reducing the viscous resistance compared to when it exceeds the upper limit. In this specification, "HTHS viscosity at 150°C" means the high temperature high shear viscosity at 150°C measured in accordance with ASTM D-4683.

The method for producing the lubricating oil composition for internal combustion engines of the present invention is not particularly limited, and the composition may be prepared by appropriately selecting and mixing each of the components to be contained so that the lubricating oil composition of the present invention can be obtained (so that the above conditions are satisfied).

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Ingredients used in each example)
First, the lubricating base oils and additives used in the examples are shown below.

<(A) Component: Lubricating base oil>
(A-1)
API Group II base oil (hydrocracked mineral base oil, Yubase® 3 manufactured by SK Lubricants), kinematic viscosity (100°C): 3.05 ^mm2 /s, kinematic viscosity (40°C): 12.3 ^mm2 /s, viscosity index: 105, NOACK evaporation amount (250°C, 1 h): 40 mass%, %C _P : 72.6, %C _N : 27.4, %C _A : 0, saturates: 99.6 mass%, aromatics: 0.3 mass%.
(A-2)
API Group III base oil (hydrocracked mineral base oil, Yubase® 4+ manufactured by SK Lubricants), kinematic viscosity (100°C): 4.2 ^mm2 /s, kinematic viscosity (40°C): 17.9 ^mm2 /s, viscosity index: 134, NOACK evaporation (250°C, 1 h): 13.5 mass%, %C _P : 87.2, %C _N : 12.8, %C _A : 0, saturates: 99.8 mass%, aromatics: 0.1 mass%
(A-3)
API Group III base oil (hydrocracked mineral base oil, Yubase® 6+ manufactured by SK Lubricants), kinematic viscosity (100°C): 6.4 ^mm2 /s, kinematic viscosity (40°C): 33.8 ^mm2 /s, viscosity index: 145, NOACK evaporation (250°C, 1 h): 8 mass%, % C _P : 85%, C _N : 15%, C _A : 0%, saturates: 99.5 mass%, aromatics: 0.2 mass%.

<Component (B): Metal-Based Detergent>
<Component (B1): Calcium-based detergent>
(B1-i)
Calcium borate overbased calcium salicylate, calcium content: 6.8% by weight, boron content: 2.7% by weight, base number (perchloric acid method): 190 mg KOH/g
(B1-ii)
Calcium carbonate overbased calcium salicylate, calcium content: 8.0% by mass, base number (perchloric acid method): 210 mg KOH/g
<Component (B2): Magnesium-based detergent>
(B2-i)
Magnesium carbonate overbased magnesium salicylate, magnesium content: 7.5% by mass, base number (perchloric acid method): 350 mg KOH/g
(B2-ii)
Magnesium carbonate overbased magnesium sulfonate, magnesium content: 9.1% by weight, base number (perchloric acid method): 400 mg KOH/g.

<Component (C): Viscosity index improver (poly(meth)acrylate-based viscosity index improver)>
(C-1)
Comb-type polymethacrylate polymer (manufactured by Sanyo Chemical Industries, Ltd., product name: Aclub V-7030, Mw: 520,000, Mn: 220,000, Mw/Mn: 2.4)
(C-2)
Linear polymethacrylate polymer (manufactured by Sanyo Chemical Industries, Ltd., product name: Aclub V-5090, Mw: 480,000, Mn: 170,000, Mw/Mn: 2.8).

<Component (D): Ashless Dispersant>
(D-1)
Non-boronated succinimide (nitrogen content: 1.6 mass%, Mw: 6000)
(D-2)
Boronated succinimide (nitrogen content: 1.2 mass%, boron content: 0.5 mass%, Mw: 7000).

<Component (E): Antioxidant>
(E-1)
Amine-based antioxidant (manufactured by BASF, product name: IRGANOX (registered trademark) L67, bis(nonylphenyl)amine, nitrogen content: 3.6% by mass)
(E-2)
Molybdenum-based antioxidant (molybdic acid dialkylamine salt, molybdenum content: 10 mass%, nitrogen content: 3.6 mass%).

<Component (F): Friction Modifier (Molybdenum-Based Friction Modifier)>
(F-1)
Molybdenum dithiocarbamate (MoDTC, manufactured by ADEKA Corporation, product name: ADEKA SAKURA-LUB 525, molybdenum content (theoretical value): 10.0% by mass).

<(G) Antiwear Agent>
(G-1)
Zinc dialkyldithiophosphate (ZnDTP, secondary alkyl group type, a compound represented by the above formula (4) in which R ¹⁴ to R ¹⁷ are each a secondary alkyl group having 4 or 6 carbon atoms, zinc content: 8.0 mass%, phosphorus content: 7.0 mass%, sulfur content: 14 mass%)
(G-2)
Zinc dialkyldithiophosphate (ZnDTP, primary alkyl group type, a compound represented by the above formula (4) in which R ¹⁴ to R ¹⁷ are all primary alkyl groups having 8 carbon atoms, zinc content: 8.0% by mass, phosphorus content: 7.0% by mass, sulfur content: 15% by mass)
(G-3)
Zinc dialkylphosphate (ZnP, primary alkyl group type having 8 carbon atoms, zinc content: 5.3 mass%, phosphorus content: 5.2 mass%).

<Component (H): Pour Point Depressant>
(H-1)
Polymethacrylate (manufactured by Evonik Industries, trade name: Viscoplex 1-300, Mw: 60,000, Mn: 32,000, Mw/Mn: 1.9).

<Component (I): Other Additives>
(I-1)
Defoaming agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KF-96H").

(Examples 1 to 3, Reference Examples 1 and 2 , and Comparative Examples 1 to 10)
The lubricating oil compositions of Examples 1 to 3, Reference Examples 1 to 2, and Comparative Examples 1 to 10 were prepared using the above-mentioned components so as to have the compositions shown in Tables 1 to 3. In the "Composition" section in Tables 1 to 3, "-" indicates that the component was not used. In addition, in the "Composition" section in Tables 1 to 3, the unit "mass%" for the content of component (A) represents the content (mass%) of each base oil component relative to the total amount of lubricating base oil, the unit "in mass%" for the content of components (B) to (H) represents the content (mass%) of each additive relative to the total amount of the lubricating oil composition, and "parts by mass" represents the proportion (parts by mass) of component (I-1) when the total mass of the components in the lubricating oil composition excluding component (I-1) is 100 parts by mass. In Tables 1 to 3, the unit "ppm by mass" of [B _(B1) ] represents the parts per million by mass (ppm by mass) of boron derived from component (B1) based on the total amount of the lubricating oil composition, the unit "ppm by mass" of [Ca _(B1) ] represents the parts per million by mass (ppm by mass) of calcium derived from component (B1) based on the total amount of the lubricating oil composition, and the unit "ppm by mass" of [Mg _(B2) ] represents the parts per million by mass (ppm by mass) of magnesium derived from component (B2) based on the total amount of the lubricating oil composition. Furthermore, in the section "Content of each element in the composition" in Tables 1 to 3, the unit "ppm by mass" for the contents of B, Ca, Mg, Mo, P, S, and Zn represents parts per million by mass (ppm by mass) of each element (B, Ca, Mg, Mo, P, S, Zn) based on the total amount of the lubricating oil composition. The values for the contents of B, Ca, Mg, Mo, P, S, and Zn in the section "Content of each element in the composition" in Tables 1 to 3 were each measured in accordance with JPI-5S-62.

[Evaluation of the properties of the lubricating oil compositions obtained in each example]
<LSPI performance evaluation test (LSPI test)>
Each lubricating oil composition was subjected to an evaluation test of LSPI suppression ability in accordance with ASTM D8291 [Test method: Sequence Nine Test (Seq. IX ASTM D8291), Engine used: Ford engine manufactured in 2012 (2000cc, 4-cylinder, GDTI engine)]. The average number of LSPI occurrences for each lubricating oil composition obtained by such measurements is shown in Tables 1 to 3 as the LSPI test results. In addition, the LSPI test results (average number of LSPI occurrences) were evaluated as to whether or not they satisfied the condition of the standard value of "5" or less of the engine oil standard "API SP/ILSAC GF-6". In Tables 1 to 3, if the result was less than the standard value (if the standard was satisfied), it was indicated as "S", and if the result exceeded the standard value (if the standard was not satisfied), it was indicated as "F". When the LSPI test result satisfies the condition of 5 or less, which is the standard value of API SP/ILSAC GF-6, the lubricating oil composition can be evaluated as having excellent LSPI suppression ability.

<SRV test (fuel economy performance evaluation test)>
Using each lubricating oil composition, a cylinder-on-disk reciprocating dynamic friction tester (SRV manufactured by Optimol) was used to perform an SRV test under the following test conditions: load: 100 N, disk temperature: 100° C., vibration frequency: 50 Hz, amplitude: 1 mm, test time: 15 minutes, and the metal-to-metal friction coefficient was measured. The results are shown in Tables 1 to 3. Note that when the friction coefficient value is 0.060 or less, it is clear that the friction characteristics are excellent, and therefore the lubricating oil composition can be evaluated as having excellent fuel saving performance.

As is apparent from the results shown in Table 1, the composition comprises (A) a lubricating base oil and (B) a metal-based detergent, the component (B) comprises a calcium-based detergent (component (B1)) and a magnesium-based detergent (component (B2)), the content of calcium derived from component (B1) is in the range of 1650 ppm by mass or more and 2500 ppm by mass or less, based on the total mass of the composition, the content of magnesium derived from component (B2) is in the range of 20 ppm by mass or more and 400 ppm by mass or less, based on the total mass of the composition, component (B1) contains component (B1-i) (a component containing boron and calcium), the total amount of B in the composition is 1000 ppm by mass or less, B _{(B1) /} Ca _{(B1 )} is 0.15 or more and 0.35 or _less , and It was confirmed that the lubricating oil compositions obtained in Examples 1 to 3 and Reference Examples 1 and 2, in which B _(B1) /[Ca _(B1) +Mg _(B2) ] was 0.13 or more and 0.29 or less, were excellent in both LSPI suppression ability and fuel saving performance (friction characteristics). The lubricating oil compositions obtained in Comparative Examples 2 and 9, in which B _(B1) /Ca _(B1) was outside the range of 0.15 or more and 0.35 or less, even though B(B1)/[Ca(B1)+Mg(B2)] was 0.29, had particularly larger friction coefficients than the lubricating oil compositions obtained in Examples 1 to 3 and Reference Examples 1 and 2 .

As described above, according to the present invention, it is possible to provide a lubricating oil composition for internal combustion engines that is capable of achieving both excellent LSPI suppression ability and excellent fuel economy performance. Therefore, the lubricating oil composition for internal combustion engines of the present invention is particularly useful as a lubricating oil composition for engines such as gasoline engines and diesel engines.

Claims (4)

(A) a lubricating base oil , ( B) a metal-based detergent , and (G) an antiwear agent ;
The component (B) is
(B1) a calcium-based detergent having a calcium content of 1,750 ppm by mass or more and 2,000 ppm by mass or less based on the total mass of the composition;
(B2) a magnesium-based detergent having a magnesium content in the range of 20 ppm by mass or more and 150 ppm by mass or less based on the total mass of the composition;
Contains
The component (B1) contains (B1-1) a calcium-based detergent containing boron and calcium,
The component (G) is a phosphorus-based antiwear agent containing zinc,
The boron content based on the total mass of the composition is 500 ppm by mass or more and 650 ppm by mass or less ,
The phosphorus content based on the total mass of the composition is 700 ppm by mass or more and 800 ppm by mass or less,
where the content of boron in component (B1) based on the total mass of the composition is represented as B _(B1) , the content of calcium in component (B1) based on the total mass of the composition is represented as Ca _(B1) , and the content of magnesium in component (B2) based on the total mass of the composition is represented as Mg _(B2) , the ratio of B _(B1) to Ca _(B1 ) (B _(B1) /Ca _(B1) ) is 0.15 or more and 0.30 or less, and the ratio of B _{(B1) to the total amount of Ca(B1)} and Mg _(B2) (Ca _(B1) +Mg _(B2) ) (B( _{B1 )} /[Ca _(B1) +Mg _(B2) ]) is 0.13 or more and 0.29 or less,
A lubricating oil composition for internal combustion engines, comprising: The lubricating oil composition for internal combustion engines according to claim 1, characterized in that the (B1) component contains calcium borate salicylate as the (B1-1) component. The lubricating oil composition for internal combustion engines according to claim 1 or 2, further comprising (C) a poly(meth)acrylate-based viscosity index improver. The lubricating oil composition for internal combustion engines according to claim 3, characterized in that the component (C) contains a comb-type poly(meth)acrylate polymer.