What solvent for parts washer?

The way to remove old petroleum by products such as caked grease, and oil/dirt is with a petroleum product. If you like to remove grease from a pan or skillet use a product that is bio-degradable.

The cheapest source is diesel fuel (not my first choice), kerosene works excellent (the fumes at first are strong) Coleman lantern fuel, (works the best, but at 15.00@gal)

I do not have a solvent tank, but use an over sized rubberized livestock tub and use it in the open. I don't like the idea of having gallons of open solvent stored in the shop area, if you go green, yea go for it.

I have never used a bio-degradable product that worked well quickly, and then required more effort with putty knife and wire brush. So work harder with the bio, or work with less effort with a solvent with all the hazards involved.