Maintenance of the engine depends heavily on regular oil changes. Allow the engine to warm up, park on level ground, and then remove the filler cap. Use a jack to raise your vehicle, let out old oil, clean an oil drain plug, and reinstall it back. Throw away an old filter, clean its surface, and put another one which is smeared with clean fuel onto it. Roll down your car, add new oil into it, and then check whether it is enough before starting your engine. Do a check for leakages, re-examine if there is enough oil in the tank again, and dispose of the waste oils properly.