There is probably not a mechanic alive that hasn’t busted his fair share of knuckles on a rusted bolt or nut. So here is a test some of the more common name brands to see how they perform.

Many mechanics will confirm that to remove rusted bolts and nuts is a real problem, but to that add spark plugs.

Yes, spark plugs.

With the extended change intervals,dis-similar metals, and carbon buildups on some engines you abdsolutely must soak the spark plugs and slowly remove them. If you don’t approach this service slowly and cautiously, the odds are that one or more will break off in the cylinder head requiring special tools to remove them or removing the head for service.

The April/May 2007 edition of Machinist’s Workshop did a test of penetrating oils where they measured the force (foot pounds of torque) required to loosen rusty test devices.

Find an old copy and buy it if you want to see how they did the test.

The results reported were interesting. The lower the number of pounds the better. Mighty interesting results for simple acetone and automatic transmission fluid mixture!

*prices are stated in 2007 US dollars
**The ATF-Acetone mix was a 50/50 mix (1 to 1 ratio).

A word of caution: Don’t put a torch on it under a car before the acetone has evaporated.

It would certainly be interesting to test some of the newer parts looseners that have come onto the market since then such as SeaFoam’s Deep Creep and others.