| abstract |
Lubricating oil composition comprising: a lubricating base oil which comprises at least one mineral base oil, at least one synthetic base oil or any mixture thereof and has a kinematic viscosity at 40°C of 5.0 to 15.0 mm 2 /s and a kinematic viscosity at 100°C of 1, 7 to 3.5 mm 2 /s; (A) a poly(meth)acrylate viscosity index improver having a weight-average molecular weight of not more than 50,000, in an amount of 2 to 10% by mass based on the total mass of the composition; (B) a phosphite ester compound represented by the following general formula (1) in an amount of 0.01 to 0.06% by mass in terms of phosphorus based on the total mass of the composition; (C) a thiadiazole compound in an amount of 0.01 to 0.2% by mass based on the total mass of the composition; and (D) a calcium salicylate detergent in an amount of 0.005 to 0.03% by mass in terms of calcium based on the total mass of the composition, wherein the lubricating oil composition has a kinematic viscosity at 40°C of 4.0 to 20.0 mm 2 /s and a kinematic viscosity at 100°C of 1.8 to 5.2 mm 2 /s; and the lubricating oil composition has a ratio [S]/[P] of 2.2 to 4.0, wherein the [S] represents a sulfur content (unit: mass %) in the lubricating oil composition and the [P] represents a phosphorus content (unit: mass %) in the lubricating oil composition represents: wherein in the general formula (1), R 1 and R 2 are each independently a group having 5 to 20 carbon atoms represented by the following general formula (2); and wherein in the general formula (2), R 3 is a straight-chain C 2-17 hydrocarbon group and R 4 is a straight-chain C 2-17 hydrocarbon group. |