"Mean Green" is one of the best cleaners I have found. Good for removing crud and grease, as long as the grease isn't caked on. A brush helps.
Be careful not to spray it on bare aluminum, however. It is mildly acidic, and will turn aluminum gray. It will also take the shine off of "almost chrome" thermal coating. Don't ask me how I found this out.
I also used it (alternating with Tide) to restore an oil soaked trunk carpet. Worked quite well, but required some scrubbing.
The industrial purple cleaner (I'll have to get the name) is similar to Mean Green, but it's lots nastier if you happen to breathe the fumes. Don't spray it on hot brakes, if you're using it for wheels/tires.