| abstract |
A lubricating oil composition for a transmission, characterized in that it comprises a base oil for a lubricating oil containing (A) a mineral oil based base oil for a lubricating oil so adjusted as to have a kinematic viscosity at 100°C of 1.5 to 5 mm2/s and a % CN of 10 to 60, and (B) a base oil for a lubricating oil having a kinematic viscosity at 100°C of 10 to 50 mm2/s and a sulfur content of 0.3 to 1 mass %, and optionally further (C) a synthetic oil consisting of carbon and hydrogen and having a number average molecular weight of 2,000 to 20,000, in respective specific amounts, and (D) an extreme pressure additive comprising a phosphorus based extreme pressure additive and a sulfur based extreme pressure additive and/or a phosphorus-sulfur based extreme pressure additive in an amount of 0.05 to 2 mass % based on the total amount of the above composition, wherein in the composition, the contents of phosphorus (P) and the total sulfur (S) are 0.01 to 0.05 and 0.05 to 0.3 mass %, respectively, and the P/S ratio is 0.10 to 0.40. The lubricating oil composition combines good fuel saving performance capability and satisfactory durability of a gear, a bearing and the like, and further is excellent in a viscosity at a low temperature and in oxidation stability. |