| abstract |
A lubricating oil composition for transmissions having improved fuel saving properties, excellent metal fatigue prevention properties, and heat resistance containing: a lubricating base oil containing (A) a mineral base oil having a 100° C. kinematic viscosity of 1.5 mm 2 /s or higher and 3.5 mm 2 /s or lower, a pour point of −25° C. or lower, a viscosity index of 105 or greater, a % C p of 85 or greater, a % C N of 2 or greater and 20 or less and a % C A of 3 or less and (B) a monoester-based base oil having a 100° C. kinematic viscosity of 2 to 10 mm 2 /s; (C) a phosphorus acid ester; and (D) a boronated ashless dispersant, the ratio of the mass percent of boron to the mass percent of phosphorus in the composition (B/P) being from 0.07 to 0.42, and the composition having a 100° C. kinematic viscosity of 2.5 to 4.0 mm 2 /s is described. |