There is much time that needs to be spent thinking about these kinds of things, yet not a second should be wasted. Then, take a bleach-based cleaning solution and scrub it down. For most materials a mix of bleach and house cleaner will do the trick. Engines get grimy but if you are thinking of pressure washing to get rid of it, please forget it. Oil change specialists suggest every 3,000 miles (4,828 kilometers) or three months.