Patent ID: 8901052

Claim:
A method of lubricating a transmission system and an electric motor, said method comprising lubricating both the transmission system and the electric motor which share a common lubrication system in an electric vehicle or a hybrid vehicle, with a single lubricant oil composition, wherein said composition consists essentially of: a base oil consisting essentially of a synthetic oil selected from the group consisting of 1-octene oligomer, a hydride thereof, 1-decene oligomer, a hydride thereof, ethylenepropylene oligomer, a hydride thereof, di-tridecyl glutarate, di-2-ethylhexyl adipate, di-isodecyl adipate, di-tridecyl adipate, di-2-ethylhexyl sebacate, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, neopentyl glycol 2-ethylhexanoate, and mixtures thereof, a phosphate compound selected from the group consisting of (B) a triaryl phosphate at 0.2 to 1.0% by mass with respect to the total composition, (C) a triaryl thiophosphate at 0.4 to 1.5% by mass with respect to the total composition, and mixtures thereof, and (D) an ashless dispersant selected from the group consisting of a nitrogen-containing compound having in its molecule at least one alkyl or alkenyl group having 12 to 400 carbon atoms, and a derivative thereof, at 10 to 400 ppm by mass in terms of nitrogen atom with respect to the total composition, wherein said ashless dispersant has a succinimide portion, wherein said composition has volume resistivity of 5×10 8 ohm·m or more at 80° C., wherein the kinematic viscosity of said composition at 80° C. is 1.5 to 3.5 mm 2 /s.