A car oil leak can destroy your engine if it’s not fixed before it gets too big. There are literally dozens of places that can leak oil on an engine. Some of these are valve covers, timing gear housing covers, oil pans, drain plugs, oil filters and rear main seals. Most of these won’t be able to leak unless the engine is running. However, oil pan gaskets, valve cover gaskets and timing gear housing covers can leak as the oil drains back to the oil pan. If your car only leaks oil while the engine is off, the most likely place to look is the oil drain plug.