The IS300 is a sports sedan that uses a rear differential to provide power to the rear wheels. The differential is lubricated by special gear oil that should periodically be replaced, and the process can easily be accomplished by an owner.
The rear differential in an IS300 contains 75W-90 gear oil, which is a standard rear differential fluid; 1.3 quarts of fluid are required. A wide variety of manufacturers produce petroleum and synthetic differential fluid in this grade and viscosity.
Some IS300s were equipped with limited-slip differentials (LSD) from the factory. For LSD-equipped cars, slip additive must be added to the fluid. Slip additive can either be added separately, or differential fluid with slip additive already incorporated can be purchased from specialty manufacturers.
The rear differential will have a drain and fill plug. Always loosen the fill plug before loosening the drain plug to assure you are not left with a inoperable vehicle should the fill plug seize or snap.
