Engine detailing is maticulous work. I don't like the idea of spraying your engine bay. although is can be done with caution. Some engines I have to use water, but whenever I can do it by hand that is thge preferred method. before you spray water on the engine do the following. I take foil (NEVER USE PLASTIC OR OTHER BURNABLE MATERIAL)I cover the electrical areas, and computer box. spray all purpose cleaner on it, use lots of shop rags and wipe down, then rinse. YOU also should have the engine running when rinsing it off. Gary p.s. wait till you see the truck from hell I detailed today. what a nightmare. will post pics soon. It made the top five of the most filthy vehicles I ever did.