[jluetjen]

I used to think that "Simple Green" was great. I had an old VW Type IV engine that was pretty gunky, so I soaked it with Simple Green and took it down to a car wash. To make a long story short, sure it took off a lot of stuff. But what it left was virtually baked on. Near as I can tell, using something like Simple Green with a water wash (even high pressure and temperature)on thick dirty grease results in the grease breaking down and the top layer of dirt coming off. Deeper down though, the build-up becomes a virtual cement when the grease wicks out. After taking the motor apart, I had a heck of a time getting that stuff off in the parts washer using mineral spirits.

If you're going to remove really thick dirt and grease, skip the Simple Green and go straight to something like mineral spirits. The dirt and varnish for the most part just floats off. If you all you have is a light coat of oil and a little dirt, Simple Green is fine.

Now how to use a solvent like Mineral Spirits with the engine in place in the engine bay is a problem that I don't have a solution to yet.

Just my $0.02