Patent ID: 8105990

Claim:
A lubricating oil composition for an internal combustion engine comprising: a lubricating base oil, comprising a saturated component having a content of 90% by mass or greater wherein a proportion of cyclic saturated components among the saturated components is 10-40% by mass; an ashless antioxidant containing essentially no sulfur as a constituent element; and at least one compound selected from among ashless antioxidants containing sulfur as a constituent element and organic molybdenum compounds; wherein the lubricating base oil satisfies a condition represented by the following formula (1) 1.440 ≦n 20 −0.002 ×Kv 100≦1.453 (1); wherein n 20 represents the 20° C. refractive index of the lubricating base oil, and Kv100 represents the kinematic viscosity at 100° C. (mm 2 /s) of the lubricating base oil.