If you want to go the extra mile........
Spend a weekend hand cleaning your engine using Simplegreen. It will remove oil/grease and built up dirt. Spend extra time removing the air cleaner and cleaning in the crevices. Make sure to cover the air inlet to your engine. Use a damp rag to remove any Simple green residue.
Once you done this you can easily maintain it with quick detailer (or water mist) and a rag. You can also use an air compressor to blow off loose dust.
I've had problems with hosing down engines on other cars and my thought is, what would cost more, replacing major electricals or spending extra time hand cleaning. The hourly cost of hand cleaning will always cost less!
02 C32 AMG
84 190E 2.3 5 Spd