Originally Posted by FP
I power wash my engine at the self wash once per month. Some use a garden hose with a 50/50 mix of water and Simple Green.
This has been the best for me as well. I also use a power washer and towel dry the every inch I can get to. If you have a really disgusting engine that has been leaking oil you may have to use a couple cans of Gum Out engine degreaser but this stuff really stinks up the car.