A lubricating oil composition for transmissions is provided which improves fuel saving properties and has excellent metal fatigue life and heat resistance. The composition contains 50 to 97 percent by mass of (A) a mineral base oil having a 100? C. kinematic viscosity of 1.5 mm.sup.2/s or higher and 3.5 mm.sup.2/s or lower, a pour point a ?25? C. or lower, a viscosity index of 105 or greater, a % C.sub.P of 85 or greater, a % C.sub.N of 2 or greater and 20 or less and a % C.sub.A of 3 or less; 3 to 10 percent by mass of (B) a monoester-based base oil having a 100? C. kinematic viscosity of 2 mm.sup.2/s or higher and 10 mm.sup.2/s or lower; and 150 to 400 ppm by mass as phosphorus of (C) a specific sulfur-containing phosphite ester. The composition has a 100? C. kinematic viscosity of 2.5 mm.sup.2/s or higher and 4.0 mm.sup.2/s or lower.

A lubricating oil composition for transmissions is provided which improves fuel saving properties and has excellent metal fatigue life and heat resistance. The composition contains 50 to 97 percent by mass of (A) a mineral base oil having a 100? C. kinematic viscosity of 1.5 mm.sup.2/s or higher and 3.5 mm.sup.2/s or lower, a pour point a ?25? C. or lower, a viscosity index of 105 or greater, a % C.sub.P of 85 or greater, a % C.sub.N of 2 or greater and 20 or less and a % C.sub.A of 3 or less; 3 to 10 percent by mass of (B) a monoester-based base oil having a 100? C. kinematic viscosity of 2 mm.sup.2/s or higher and 10 mm.sup.2/s or lower; and 150 to 400 ppm by mass as phosphorus of (C) a specific sulfur-containing phosphite ester. The composition has a 100? C. kinematic viscosity of 2.5 mm.sup.2/s or higher and 4.0 mm.sup.2/s or lower.

To provide a lubricating oil composition for internal combustion engines, which can realize low friction in both internal combustion engines equipped with a DLC and internal combustion engines not equipped with a DLC. [Solution] a lubricating oil composition for internal combustion engines, which is characterized in that the lubricating oil composition for internal combustion engines is a composition obtained by blending a molybdenum dithiocarbamate (MoDTC) and a polyalkylene glycol (PAG) in a base oil, the weight average molecular weight of the polyalkylene glycol is 2750-4500 and the content of the polyalkylene glycol is not less than 0.05 mass % and less than 10 mass % relative to the total mass of the composition.

To provide a lubricating oil composition for internal combustion engines, which can realize low friction in both internal combustion engines equipped with a DLC and internal combustion engines not equipped with a DLC. [Solution] a lubricating oil composition for internal combustion engines, which is characterized in that the lubricating oil composition for internal combustion engines is a composition obtained by blending a molybdenum dithiocarbamate (MoDTC) and a polyalkylene glycol (PAG) in a base oil, the weight average molecular weight of the polyalkylene glycol is 2750-4500 and the content of the polyalkylene glycol is not less than 0.05 mass % and less than 10 mass % relative to the total mass of the composition.

(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.

The present invention provides a lubricating oil composition comprising: a lubricating base oil; 1.0% by mass or more and 15.0% by mass or less of a dispersant poly(meth)acrylate compound having the weight average molecular weight of 20000 or more and 200000 or less; 0.05% by mass or more and 6.0% by mass or less of a thiadiazole compound; 1.5% by mass or more and 4.0% by mass or less of a polysulfide compound; and 0.2% by mass or more and 1.5% by mass or less of a friction modifier, based on the total amount of the lubricating oil composition, wherein the mass ratio of the polysulfide compound content to the thiadiazole compound content (polysulfide compound/thiadiazole compound) is 0.4 or more and 50 or less, and the kinematic viscosity at 100 C. of the lubricating oil composition is 7.0 mm.sup.2/s or more and 35.0 mm.sup.2/s or less.

The present invention provides a lubricating oil composition comprising: a lubricating base oil; 1.0% by mass or more and 15.0% by mass or less of a dispersant poly(meth)acrylate compound having the weight average molecular weight of 20000 or more and 200000 or less; 0.05% by mass or more and 6.0% by mass or less of a thiadiazole compound; 1.5% by mass or more and 4.0% by mass or less of a polysulfide compound; and 0.2% by mass or more and 1.5% by mass or less of a friction modifier, based on the total amount of the lubricating oil composition, wherein the mass ratio of the polysulfide compound content to the thiadiazole compound content (polysulfide compound/thiadiazole compound) is 0.4 or more and 50 or less, and the kinematic viscosity at 100 C. of the lubricating oil composition is 7.0 mm.sup.2/s or more and 35.0 mm.sup.2/s or less.

A problem is to provide a heat treating oil composition containing a sulfur compound that is excellent in brightness of a metal material after a heat treatment, such as quenching, and in storage stability. The problem is solved by a heat treating oil composition containing one or more kinds of base oils (A) selected from the group consisting of a mineral oil (A1), a synthetic oil (A2), and a vegetable oil (A3), and a sulfur compound (B), the sulfur compound (B) containing one or more kinds selected from the group consisting of a particular sulfide compound (B1), a particular sulfide compound (B2), and a particular thiazole compound (B3).

The invention provides a grease composition for rolling bearings that can exhibit improved bearing life that can secure the low noise performance under high temperature conditions, and a rolling bearing where the above-mentioned grease composition is enclosed. The grease composition for rolling bearings includes a base oil, a urea thickener and a metal deactivator. The base oil has an aniline point of 110 C. or more. The urea thickener is at least one kind of diurea compound selected from the group consisting of diurea compounds represented by formula (1): R.sup.1NHCONHR.sup.2NHCONHR.sup.3 (wherein R.sup.1 and R.sup.3, which may be the same or different from each other represent a C.sub.6-30alkyl group, a C.sub.5-8cycloalkyl group or a C.sub.6-10aryl group, and R.sup.2 represents a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms.)

The invention provides a grease composition for rolling bearings that can exhibit improved bearing life that can secure the low noise performance under high temperature conditions, and a rolling bearing where the above-mentioned grease composition is enclosed. The grease composition for rolling bearings includes a base oil, a urea thickener and a metal deactivator. The base oil has an aniline point of 110 C. or more. The urea thickener is at least one kind of diurea compound selected from the group consisting of diurea compounds represented by formula (1): R.sup.1NHCONHR.sup.2NHCONHR.sup.3 (wherein R.sup.1 and R.sup.3, which may be the same or different from each other represent a C.sub.6-30alkyl group, a C.sub.5-8cycloalkyl group or a C.sub.6-10aryl group, and R.sup.2 represents a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms.)