Differential fluid lubricates the differential in all-wheel drive (AWD), four-wheel drive (4WD), rear-wheel drive (RWD), and front-wheel drive (FWD) vehicles. In most cases, front-wheel drive vehicles have a transaxle instead of a separate differential, but there are some instances where FWD vehicles have a stand-alone differential. The purpose of the differential is to deliver power to the wheels while allowing them to turn at different speeds. As your vehicle completes a turn, each wheel covers a different distance. The two wheels on the inside of the turn travel a shorter distance than the two wheels on the outside of the turn. Similarly, the two front wheels travel a different distance than the two back wheels. The differential allows your vehicle to make turns smoothly despite these differences, and differential fluid keeps the moving parts of the differential lubricated. Your differential needs clean differential fluid to ensure a smooth ride at all times.