I had a throwaway garage-sale glove and decided to try out synthetic motor oil as a conditioner. I followed my normal cleaning procedure of fast-orange with pumice and let it dry for more than a month. I poured about a cup of Mobil 1 full-synthetic (10W-30) into a large bowl and dabbed a wad of paper towels in the oil. I rubbed the glove down with the paper towels until it was completely covered. I did this a few times until the glove was uniformly wet. The results were very good. The oil darkened the glove about as much as petroleum jelly, but didn't leave the glove greasy. The glove started out as a board, and is now fully playable. Oh, I also relaced it. I forgot to take before photos, but here are the after photos: