Originally Posted by gunrunnerjohn:
... After a year or two, it turns into some sort of sludge-like varnish that is almost impossible to remove! I've had to soak guns for a week in solvent to loosen the WD-40 before I could even disassemble them!
IMO, it fails miserably as a lubricant.
I wonder if the WD-40 may have partially dissolved other old oils or cosmoline which redistributed and re-solidified in different places after the WD-40 dried out? I haven't experienced WD-40 itself turning into a "sludge-like varnish". Just interested.
I consider WD-40 to be a penetrant and "temporary" lubricant, as for removing rusty bolts.