Bill Houghton, Sebastopol, CA
I had a small container of art store turpentine a while back, and was amazed to find how well it cut grease, compared to mineral spirits.

I haven't looked lately to see if my hardware store even stocks turpentine. They've taken to stocking a mineral spirits substitute that is just awful; I've been buying every can of real mineral spirits I find at yard sales, even if it's only partly full.