Penetrating Oil

 Maybe 60 years ago I bought a can of penetrating oil, Rust Aid by Detroit Efficiency Company. That was the best I had ever had, and have never found any sense of the same. What is the best can be bought today ?

While not as good as atf/acetone mix, Kroil works well. PB Blaster is a distant 3rd.
WD40 is around 80th place.

WD40 is a rust preventative, not a penetrating oil. I like blaster, but I think heat penetrates the best.

CRC makes a product called Knock er Loose. You can get it at most auto parts stores, bad thing with it is that once you start using the can the spray pressure disappears in about a month then you have to squeeze the can to continue using it but works great and not bad smelling. There is also a product called freeze off that CRC makes that works good too, it uses a penetrating oil and extremely cold air in a can to loosen stuff

I have a friend who swears by iodine. Have not tried it myself.  

In my opinion, there all about the same- just a little oil lube in a simple spray can, we got that kroil at work - expensive,, 

my new thing is free all , i have been using that for about a year or two ithink its the best rust buster penitrating oil i have ever used but much for lubricating .  the better lubricating penatrating oil that i have useing is shaffers pentro90 . istill use texas refineries essental lube for penitrating oil when i am heating parts with the torch it really thats alot of heat 

I do like WD40 because of the straw feature on the can. As for best product, I don't really care! In some situations any lubricant would work. In other situations your using a cut off wheel or the "Hot Wrench"!

Darwin W. Kurtz wrote: make your own with 1/2 automatic trans fluid and 1/2 paint thinner. A salvage yard man told me they had freed stuck motors with this combination

2x.

Definitely add heat for toughest items. If possible, try to heat the item that you’d like to expand. If you can’t expand the ideal part, then Heat will transfer very well on attaching part(s). One time I was able to successfully remove a corroded semi truck’s engine starter mount bolt by heating the bolt’s head(only piece I could access with torch heat). It was a Steel bolt threaded into an aluminum transmission bell housing ~ so decades of corrosion between different metals. Took two heat cycles(dull red color). Heat up, let cool, do again.

I think the MAP gas torches produce more heat.

This link explains MAPP Gas. To get a heat hot enough Oxygen is required. https://en.wikipedia.org/wiki/MAPP_gas

I thought WD 40 is a moisture displacement. Try 50% ATF, 50% Acetone, season to taste, heavily slather on some brake fluid, again season to taste, and let her rip. The acetone will evaporate quickly, so act accordingly. Pour it in the toilet if stomach pains occur. See a Doctor either Jill or Kamala if erections last more than 4 hours. Should you land nose first get it as hot as you can and melt a candle on it.

Thanks Jim . That would be nice to have !