Oil Filler Cap
The oil filler cap is a plastic or metal cap that covers an opening into the valve cover. It allows you to add oil when the dipstick indicates that you need it. If you have a look at your engine you should be able to easily notice the cap. This is a handy cap to remember as you are recommended to check and add oil to your car on a regular basis. Some cars have the crankcase vented through the filler cap. Oil which is added through the filler passes down through openings in the head into the oil sump at the bottom of the engine.