"Penetrene" is pretty good. Give it two hits over 24 hours, only thing is the plastic bottle it comes in really only lets you apply it from the top down once it's about half empty (a small brush works though) . Harder to get now but Blackwoods still carried it last year when I bought the last bottle, $16 for 500 mills. But you don't use much. just a few drops and let it creep down the thread from the top.