any parts degreaser solvent recommendations

[Ben Swann]

I just got a 50 gal parts washer to clean engine parts.  I found the cost of the mineral spirit based degreaser to be rather expensive.  Recommendations for an economical solvent or degreaser?  Looks like I'll need at least 20 gallons.

I suppose an online source that can ship me the stuff in 5 gal. containers would be good.  Just need a less expensive source.

Ben