I use the Turtle Bug and Tar cleaner on my car's . Then re wax the area. Simple green really screwed up the decal's and sticker's on the engine on a car I had many year's ago. Will not use it on anything since. The best thing I have found to clean dirt and grease off with and won't hurt anything is Bike Brite . You can get it at most Motorcycle shop's . I used it on my Harley for 7 year's . Clean's those hard to get at place's . Spray on and hose off . Then with a stream of water nor spay . To get it all off . Then I take my leaf blower to blow the water off for a spot free shine. It does not hurt rubber either. Or paint.