Patent ID: 11111455

Abstract:
The invention provides a lubricating oil composition for automatic transmissions is made such that it comprises proportionately as its main constituents: 60 to 98 mass % as low viscosity base oils being base oils belonging to Groups 2 to 4 of the API (American Petroleum Institute) base oil categories wherein the kinematic viscosity at 100° C. is 2 to 5 mm2/s (Fischer-Tropsch synthetic oil comprising at least 45 to 80 mass %); 1 to 20 mass % as high-viscosity base oils being metallocene/poly-α-olefins with a kinematic viscosity at 100° C. of 100 to 600 mm2/s; and 1 to 20 mass % being a polymethacrylate with a weight-average molecular weight of 10,000 to 50,000. The viscosity index of this composition is not less than 190, the Brookfield viscosity at −40° C. is not more than 5000 mPa·s, the 100° C. kinematic viscosity is 5 to 7 mm2/s, and the rate of reduction of the 100° C. kinematic viscosity after a KRL shear stability test (60° C., 20 hr) is not more than 3%.