This is a question that I get all the time during my car maintenance and repair career. If you notice your car is losing oil but not leaking, it could be one of several issues. A common problem for your car to leak oil is a worn piston ring. The piston ring is the rubber seal that keeps oil in and combustion gases out of the engine. A worn piston ring allows oil to escape from the engine, but it does not always allow gas to escape.