ATF acetone is a 50/50 mix of Automatic Transmission Fluid and Acetone. One of the best penetrating concoctions for breaking free stuck/corroded metal parts. "Kano Kroil Oil" is another option and probably less expensive if you don't have the other two products on hand. There is/was a seller on Ebay selling little 1oz. bottles of Kroil for cheap. I've had one for about 10 years and it's still 3/4 full. A little goes a long way.