We use plain old mineral spirits(paint thinner) in our parts washer. It works good for what we clean which is mainly old engine parts. For things that won't fit in the parts washer we use Greased Lightning and a pressure washer, it works good but it makes you gag. We have also used some cleaner from the NAPA store, I think it's called awesome orange and it works pretty good too. In the end, the best thing is whatever works for you.
