answer:I throw them out. I may keep one if it’s not too bad, for around the house, paint projects, etc. Seriously, life is too short to wear stuff that looks like crap. Also, my house is too small to keep stuff that I can’t wear, so in the dumpster it goes. To answer your question, usually it’s almost impossible to get a real grease stain out. You can try soaking it in a pre-wash treatment but it’s not likely to be entirely gone.