The invention addresses a problem of providing a lubricating oil composition for gas engines capable of suppressing viscosity increase while reducing a sulfated ash content and excellent in high-temperature detergency and base number retention. The lubricating oil composition is used for gas engines and contains a base oil (A), at least one ash-free additive (B) selected from an ash-free sulfur-based antioxidant (B1) and a hindered amine compound (B2), and a boronated imide-type dispersant (C), and satisfies the following requirements (X1) to (X3): Requirement (X1): the sulfated ash content is 0.2% by mass or less. Requirement (X2): the content of the ash-free additive (B) is 1.2% by mass or less based on the total amount of the lubricating oil composition, provided that in the case where the ash-free additive (B) contains the hindered amine compound (B2), the content of the hindered amine compound (B2) is less than 1.0% by mass based on the total amount of the lubricating oil composition. Requirement (X3): the content of the boron atom derived from the boronated imide-type dispersant (C) is 200 ppm by mass or more based on the total amount of the lubricating oil composition.

The invention addresses a problem of providing a lubricating oil composition for gas engines capable of suppressing viscosity increase while reducing a sulfated ash content and excellent in high-temperature detergency and base number retention. The lubricating oil composition is used for gas engines and contains a base oil (A), at least one ash-free additive (B) selected from an ash-free sulfur-based antioxidant (B1) and a hindered amine compound (B2), and a boronated imide-type dispersant (C), and satisfies the following requirements (X1) to (X3): Requirement (X1): the sulfated ash content is 0.2% by mass or less. Requirement (X2): the content of the ash-free additive (B) is 1.2% by mass or less based on the total amount of the lubricating oil composition, provided that in the case where the ash-free additive (B) contains the hindered amine compound (B2), the content of the hindered amine compound (B2) is less than 1.0% by mass based on the total amount of the lubricating oil composition. Requirement (X3): the content of the boron atom derived from the boronated imide-type dispersant (C) is 200 ppm by mass or more based on the total amount of the lubricating oil composition.

Provided is a lubricating oil composition, which has low viscosity but also prolonged anti-shudder life without reduction of intermetallic friction coefficient. The lubricating oil composition is characterized in comprising (A) a lubricating base oil, and (C) (C-1) a borated succinimide compound with a mass average molecular weight of 4,000-7,000 and (C-2) a borated succinimide compound with a mass average molecular weight of greater than 7,000-10,000.

The present invention relates to the use as an antiwear additive (antiwear component) and friction modifier in a lubricant of at least one compound having the following formula (I) wherein: each of R and R, which are identical of different, is a aliphatic group preferably containing between 5 and 23 carbon atoms; and a and b are integers from 0 to 4; and A is a methylene group CH.sub.2; or a carbonyl group C(?O).

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The present invention relates to the use as an antiwear additive (antiwear component) and friction modifier in a lubricant of at least one compound having the following formula (I) wherein: each of R and R, which are identical of different, is a aliphatic group preferably containing between 5 and 23 carbon atoms; and a and b are integers from 0 to 4; and A is a methylene group CH.sub.2; or a carbonyl group C(?O).

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(1) A cylinder lubricating oil composition for a crosshead diesel engine, the composition having a sulfated ash content of 2.0 to 5.5 mass %; a base number of 15 to 45 mgKOH/g; and an autoignition temperature of no less than 262? C. (2) A cylinder lubricating oil composition for a crosshead diesel engine, comprising: a lubricant base oil; (B) a Ca sulfonate detergent having a base number of no less than 10 mgKOH/g and less than 60 mgKOH/g; (C) a Ca phenate detergent having a base number of 55 to 200 mgKOH/g; (D) an amine antioxidant; and (E) a zinc dithiophosphate, wherein the composition has a base number of no less than 15 mgKOH/g and less than 120 mgKOH/g.

Disclosed is a dispersant composition, suitable for use in lubricating oils. The dispersant composition is a reaction product of (i) a polyalkenyl succinimide post-treated with a post-treating agent selected from the group consisting of an organic carbonate, an epoxide, a lactone, a hydroxyaliphatic carboxylic acid, and combinations thereof; and (ii) an acylating agent.

The invention relates to a method of lubricating an internal combustion engine comprising supplying to the engine a lubricating composition comprising: an oil of lubricating viscosity, 2.3 wt % to 4 wt % of a dispersant package, wherein the dispersant package comprises: a borated succinimide dispersant obtainable by an ene reaction of a polyalkylene with an acylating agent to form an intermediate, reacting the intermediate with an aminoalcohol or amine to form a dispersant, and reacting the dispersant with a borating agent to form a borated succinimide dispersant; and a non-borated succinimide dispersant obtained by a Diels-Alder reaction. The ratio of non-borated succinimide dispersant to borated succinimide dispersant is 90:10 to 20:80, and the borated succinimide has 0.2 wt % to 1.3 wt % boron on an oil-free basis of the dispersant.

The invention relates to a method of lubricating an internal combustion engine comprising supplying to the engine a lubricating composition comprising: an oil of lubricating viscosity, 2.3 wt % to 4 wt % of a dispersant package, wherein the dispersant package comprises: a borated succinimide dispersant obtainable by an ene reaction of a polyalkylene with an acylating agent to form an intermediate, reacting the intermediate with an aminoalcohol or amine to form a dispersant, and reacting the dispersant with a borating agent to form a borated succinimide dispersant; and a non-borated succinimide dispersant obtained by a Diels-Alder reaction. The ratio of non-borated succinimide dispersant to borated succinimide dispersant is 90:10 to 20:80, and the borated succinimide has 0.2 wt % to 1.3 wt % boron on an oil-free basis of the dispersant.

The present invention provides an engine oil composition including 70 to 95 percent by weight of a base oil and 0.01 to 15 percent by weight of a dispersant comb polymer, based on the overall weight of the engine oil composition. The dispersant comb polymer consists of 13.7% by weight of a macromonomer, which is an ester of methacrylic acid and a hydroxylated hydrogenated polybutadiene with Mn of 4750 g/mol; 51.5% by weight of n-butyl methacrylate; 17.3% by weight of LMA; 11.2% by weight of styrene; 0.2% by weight of methyl methacrylate; and 6.10% by weight of N,N-dimethylaminoethyl methacrylate. The modified dispersant inhibitor package contains 30 wt % or less of succinimide type dispersant based on the overall weight of the modified dispersant inhibitor additive package, and the engine oil composition has an SAE viscosity grade of 0W-X, wherein X is 30 or less.