I never degrease my engine anymore... on my old 92 camaro when I had it I tried to degrease and spray down the engine and it didn't start for like 4 hours... freaked me out, and since then it had problems in the rain with stalling out. You should be fine though, because that car was old, and I also know people who do it all the time and it works good. As far as spraying it n a warm engine i dont know because degreaser is very flammable.