The chart originated, if I recall, with Machinist's Workshop Magazine quite a number of years ago. Other tests have been done since then, and the results vary.
(For example -
).
[Spoiler - the Liquid Wrench won, followed by the Acetone-ATF combination, but heat did better than both].
Different products do well in different circumstances. Each test is a little different. But there seem to be a few recurring lessons:
- Any product within a mile of correct for the task is better than nothing.
- When you can apply it, heat helps if it's a steel-steel joint.
- The Acetone-ATF thing is not a myth, it actually does help if the circumstances are correct.
- Liquid Wrench and Kroil cycle in and out of favor, depending on the test, but again, it's better than doing nothing.
- WD-40 tends to work better as a preventative than a penetrating oil, but is still better than nothing.
- The smell of PB Blaster comes up as a complaint occasionally.
I would use Kroil or Liquid Wrench over ATF/Acetone where you are dealing with a painted area, where you are applying any more than minimal heat, and if you are doing a longer term soak. Acetone/ATF is great if you don't have to deal with paint, can't apply heat, and want to go straight at it.
My go-to, if given the choice, is heat and Kroil or heat and Liquid Wrench. I apply the oil, heat gradually until it starts to bubble in the joint, then apply a little more oil and let cool. But I've also used ATF/Acetone and it works nicely when the circumstances are right.