Lubricating oil composition

A method of cooling an electric vehicle device, comprising:

• applying a lubricating oil composition comprising a base oil to an electric vehicle device,
• wherein the base oil comprises an ester-based synthetic oil such that the content of the ester-based synthetic oil is in a range of 30% by mass to 100% by mass based on the total amount of the base oil, the ester-based synthetic oil is at least one selected from the group consisting of a first ester of a first monohydric alcohol and a monobasic acid and a second ester of a second monohydric alcohol and a polybasic acid, the first monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, the monobasic acid includes a fatty acid having 6 to 8 carbon atoms, the second monohydric alcohol has a carbon number of 1 to 8 and has no aromatic group, the polybasic acid includes a dibasic acid having 4 to 8 carbon atoms and having no aromatic group, the base oil has a flash point of 105° C. or higher and 200° C. or lower according to a Cleveland open-cup method, a kinematic viscosity in a range of 2.00 mm2/s to 4.00 mm2/s at 40° C., a specific heat of 1.75 KJ/(kg·K) or less at 20° C., and a density of 0.850 g/cm3 or more at 20° C. and the electric vehicle device is at least one selected from motors, generators, electric storage devices, converters, inverters, engines and transmissions.

A cooling system for cooling an electric vehicle device, comprising:

• a lubricating oil composition comprising a base oil,
• wherein the base oil comprises an ester-based synthetic oil such that the content of the ester-based synthetic oil is in a range of 30% by mass to 100% by mass based on the total amount of the base oil, the ester-based synthetic oil is at least one selected from the group consisting of a first ester of a first monohydric alcohol and a monobasic acid and a second ester of a second monohydric alcohol and a polybasic acid, the first monohydric alcohol includes at least one selected from the group consisting of methanol, ethanol, and octanol, the monobasic acid includes a fatty acid having 6 to 8 carbon atoms, the second monohydric alcohol has a carbon number of 1 to 8 and has no aromatic group, the polybasic acid includes a dibasic acid having 4 to 8 carbon atoms and having no aromatic group, and the base oil has a flash point 105° C. or higher and 200° C. or lower according to a Cleveland open-cup method, a kinematic viscosity in a range of 2.00 mm2/s to 4.00 mm2/s at 40° C., a specific heat of 1.75 KJ/(kg·K) or less at 20° C., and a density of 0.850 g/cm3 or more at 20° C.