Never fails, there’s always one...

[Paul Workman]

Originally Posted by XfireZ51

Kroil is the only penetrant that has broken loose every nut and bolt I have tried it on. PB Blaster doesn't come close.

Dittos! It comes in a liquid or a spray too!

(Kroil is well known to competition rifle teams too. Kroil will cut through carbon and get under copper fouling and release its adhesion to the bore of match grade barrels...but I digress.)

UPDATE:

FOR WHAT IT'S WORTH...ON another forum, someone suggested that a mixture of ACETONE (aka fingernail polish remover) and ATF (proportions not given) works much better than any of the common commercial penetrants.