Common reasons for oil leaks in cars include worn out gaskets or seals, damaged oil pan, faulty valve cover gasket, or a damaged oil filter. To repair these leaks, the damaged parts must be replaced or repaired, and new gaskets, seals, or filters must be installed. In some cases, a mechanic may need to use a sealant to stop the leak. It is important to address oil leaks promptly to prevent damage to the engine and maintain the proper levels of oil.