Question about that old trick of using ATF and acetone as a penetrating oil

So my grandpa always swore by mixing automatic transmission fluid with acetone for seized bolts. Said it works better than anything you can buy. I tried it on a rusted exhaust manifold bolt on my '65 Mustang last weekend and it worked like magic. But then my buddy at the car meet said I'm basically just wasting acetone and ATF, and that modern penetrants like PB Blaster are actually better. I got the bolt loose but I'm wondering if it was the mix or just luck. Has anyone actually tested both side by side or is this just one of those old timer things that stuck around for no reason?

2 comments

2 Comments

the_karen15d ago

His buddy said PB Blaster is better than Grandpa's ATF mix?

oliver24214d agoTop Commenter

Heard a guy on another forum say he tested both side by side on a seized exhaust bolt and the ATF mix actually worked faster. Something about the acetone letting it creep into tighter spots than PB can. Makes sense because the ATF mix is thinner, it just drips everywhere if you're not careful. PB Blaster is fine for general stuff but that old school mix has a reputation for a reason. I keep a spray bottle of ATF and acetone around for anything really stuck.