To clean my engine, I use Simple Green, full strength, applied from a spray bottle, like an empty Windex spray bottle. I use this on all my car’s engines when I first buy a car, doing it about once a month or so. My engines always look new, even after 5 years. Simple Green gets most of the crud off if I let it sit, then I spray it with off with a hose, taking care to not spray directly on the electronics or the dip sticks. If your engine has thick road grime and old grease on it, Simple Green won’t help. You’ll need a professional steam cleaning.