Penetrol, can get it at Lowes or Home depot. Will last a complete season if you do not hit it with a pressure sprayer. After winter, I usually take mine to car was and use high pressure sprayer and remove the coating and wash the jeep really good. Let it dry all the way and then I will use a foam applicator and apply a coat to all fenders. Be prepared not to drive for at least half a day since this takes a while to dry. Another trick is to use surgical gloves and put a sock over the glove and you can apply the same stuff to metal bumpers, plastic mirror frame, bumper ends and just about anything that gets dull. Be very careful not to get it on the paint cause is will turn a little dark over time if you do. Looks bad on a light color paint.