Shell Oil Comapny

Shell Internationale Research Maatschappij, B.v.

Genki Kamei

Ryuji Maruyama

Shouhei Harada

Kengo Suzuki

Shinji Saitou

This invention provides a lubricating oil composition for automobile transmission that includes: as low-viscosity base oils: (i) between 45 and 95 mass % of a Fischer-Tropsch synthetic low-viscosity base oil with a 100&#xb0; C. kinematic viscosity of between 1 mm/s and 2 mm/s, and between 0 and 25 mass % of other than a Fischer-Tropsch synthetic low-viscosity base oil with a 100&#xb0; C. kinematic viscosity of between 1 mm/s and 2 mm/s, and (ii) between 0 and 35 mass % of a base oil wherein the 100&#xb0; C. kinematic viscosity is greater that 2 mm/s and no greater than 5 mm/s; and (iii) between 5 and 55 mass % of an olefin polymer or copolymer, as a high-viscosity base oil, wherein the 100&#xb0; C. kinematic viscosity is between 100 and 800 mm/s. A lubricating oil composition for an automatic transmission wherein the 100&#xb0; C. kinematic viscosity of this composition is between 3.8 and 5.5 mm/s, the viscosity index is no less than 190, the flashpoint is no less than 140&#xb0; C., and the reduction ratio of the 100&#xb0; C. kinematic viscosity after shear stability testing, at 60&#xb0; C. for 20 hours, is maintained at no greater than 3%.

Lubricating oil composition for automatic transmission

The present invention provides a lubricating oil composition for automatic transmissions which comprises: 55 to 85 mass % of a Fischer-Tropsch synthetic oil with a kinematic viscosity at 100&#xb0; C. of 2 to 4 mm2/s as a low-viscosity base oil; 1 to 10 mass % of an olefin copolymer 5 with a kinematic viscosity at 100&#xb0; C. of 150 to 1,000 mm2/s as a high-viscosity base oil; and a polymethacrylate with a weight-average molecular weight of 10,000 to 50,000. This lubricating oil composition is such that the viscosity index of the composition is not 10 less than 190, the Brookfield viscosity is not more than 6,000 mPa&#xb7;s at low temperature (&#x2212;40&#xb0; C.), the kinematic viscosity at 100&#xb0; C. is 6 to 7 mm2/s, and the rate of reduction of the kinematic viscosity after a KRL shear stability test (60&#xb0; C., 20 hr) is kept to within not more 15 than 3%.

Lubricating oil composition for automatic transmissions

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&#xb0; C. is 2 to 5 mm/s (Fischer-Tropsch synthetic oil comprising at least 45 to 80 mass %); 1 to 20 mass % as high-viscosity base oils being metallocene/poly-&#x3b1;-olefins with a kinematic viscosity at 100&#xb0; C. of 100 to 600 mm/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 &#x2212;40&#xb0; C. is not more than 5000 mPa&#xb7;s, the 100&#xb0; C. kinematic viscosity is 5 to 7 mm/s, and the rate of reduction of the 100&#xb0; C. kinematic viscosity after a KRL shear stability test (60&#xb0; C., 20 hr) is not more than 3%.

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Tokyo, Japan

Genki Kamei