| 摘要 |
Disclosed is a transmission fluid composition having a kinematic viscosity at 100°C of 2-10 mm2/s and a viscosity index of not less than 150, wherein the kinematic viscosity and the NOACK evaporation loss satisfy the following relation (I): X/3 + Y <= 6.33 (I) (wherein X represents the kinematic viscosity (mm2/s) at 100°C and Y represents the NOACK evaporation loss (mass%) in 1 hour at 200°C). Also disclosed is a transmission fluid composition comprising a base oil which contains at least one substance selected from an alpha-olefin oligomer obtained by oligomerizing an alpha-olefin by a specific method, a hydrogenated product of such an alpha-olefin oligomer and the like. Such transmission fluid compositions have low viscosity, extremely low evaporation loss, long metal fatigue life such as pitting resistance, high viscosity index, good low-temperature fluidity, good extreme pressure properties and good oxidation stability. Consequently, the transmission fluid compositions are suitable for various transmissions, in particular for automatic transmissions. |
