Transmission fluid

Abstract

Implementations of the disclosed subject matter provide a lubricating composition for use as a transmission fluid in an electric vehicle. The lubricating composition may include at least 70 wt %, based on the overall weight of the lubricating composition, of a biodegradable ester base oil with a kinematic viscosity at 100° C. in the range of 2.5 to 7.0 mm2/s. The ester is biodegradable according to OECD test guidelines series 301. The composition may also include at least 0.5 wt % and no more than 10 wt %, based on the overall weight of the lubricating composition, of a viscosity index improver which is at least one high viscosity ester with a kinematic viscosity at 100° C. of at least 1000 mm2/s; an anti-foam additive selected from silicone oil based antifoam additives and polyacrylate antifoam additives. Also disclosed is a process for lubricating an electric vehicle drive train comprising a transmission by applying the lubricating composition to the transmission.

Dependencies are inferred from the claim text.