RobT2K,
I think its the foamy Gunk that says that. The only reason I could find is that if the engine is hot, the Gunk will slide right off. But if its cool or slightly warm it will stick for a couple minutes to eat through the grease.

 

I use either simple green or greased lightning all purpose cleaner. I just spray it on, let it soak for about 10 minutes and spray the engine down. THe only thing i try to avoid is hiting the airbox with the hose. Other than that I just blast it. It cleans up pretty well. I don't use Gunk because the smell makes me sick I've noticed that it smells even when you hose it off so I just avoid that.

 

ive heard that simple green does some sort of damagte to engine long term...i think it causes premature hose failure, and i knwo there is something else...