Simply put, engines demand so much from the use of oil that eventually the chemical construction of the motor oil breaks down and can no longer provide good lubrication. Oil is used in cars to lubricate the engine and drive train system. Lubrication is important to prevent premature wear especially in high performance engines. Further, variable timing is dependent on the correct oil pressure applied to these units via small ports to create energy. Not only is it important to replace the oil, it is important to use good OEM oil that will insure against wear. This is especially so with high performance engines, stop-start systems and turbo charges and has advantages for vehicles fitted with exhaust after treatment systems such as catalysts or particulate filters.