P21S cycle wash is safe for all surfaces. I saw Meguiars Hyper dressing used (diluted 4 to 1)
on a slightly warm cleaned engine. Just wash it down with cleaner of your choice, liberally spray the Hyper Dressing all over, close the hood, and come back in an hour. The engine bay looks perfectly detailed no matter the surface, has no sticky or slick feel, and won't harm paint, plastic, rubber or alloys. The trick is make sure the engine is warm, but not hot.
Going to pick some up from my local dealer next time I do some engine cleaning. No connection to Meguiars - just looked like a great time saver.<ul><li><a href="http://www.meguiars.com/?detailer-dressings/Hyper-Dressing">http://www.meguiars.com/?detailer-dressings/Hyper-Dressing</a</li></ul>