Parts that are really caked-up with grime should be scraped with a plastic knife or similar item that won't make scratches.

Soaps meant for dish washing machines usually contain amonia and are much stronger than soaps meant for hand dish washing. In fact, you should never use dish wash machine soap on good paint.

Strong dish washer machine soap, an old toothbrush, plus very hot water works very good. And it's free, and you don't have to take time off from playing with your car to go get some - just open the cabinet door under the sink, and there it is!

Just be sure to clean up the kitchen sink before wifey sees it.