Originally Posted by ljnlaw

I generally get a nonabrasive cleaner like Simple Green and spray down the engine compartment and use a soft brush to wipe away loose dirt and grime. Lightly hose down the engine bay and then use your favorite rubber conditioner (Meguiar's, Armor All, etc.) to squirt down the hoses and black plastic covers. Then start the car and let the engine run for 5 minutes and it should look brand new. I have used this simple method for over 20 years and never had any problems.