I work on/restore old cars/trucks & boats (into trucks right now and another old boat).An old guy turned me onto Deep Creep a few years ago when I couldn't get a cast iron threaded 4" exhaust flange loose that hadn't been removed since 1952 when Chris Craft installed the motor. I had been using PB Blaster and some heat. I used the Deep Creep and got it and the 4 bolts screwed into the end of the exhaust manifold loose without breaking any off. With any penetrating fluid, patience is the key. Sometimes it takes a few days.