Re: It's the Internet
The problems with WD40 are that:
1. It's getting *&*&$£))" expensive for a gas powered small can of thin oil diluted by the 'merkin equivalent of white spirit.
2. It's just that, a a diluted thin oil, not a multipurpose cure - all, which is what it's sold as. For example it is NOT a penetrating oil to help free rusted up fastenings, but it will penetrate up to a point.
For what it is, a dewatering agent which evaporates to leave a mineral oil film it's ok - handy to have a tin around in the workshop / toolbox / motor in case of need.
For any serious use you need a specialist product. (Unfortunately, many specialist products are no better - just more expensive.)
Re penetrating oil - the idea is to have a very thin low surface tension carrier which penetrates between the stuck threads by wetting and capillary action, and carries with it a very small quantity of lubricant. White spirit will do up to a point - it's a bit better than thick oil, that's all.
Try comparing Laco Rustbuster with WD40 for example. The Laco is so much better. Peoples on the interwebbs suggest a mixture of acetone and auto transmission fluid. Acetone has a very low surface tension, and auto transmission fluid presumably has good extreme pressure lubrication properties, so it kinda makes sense. Being an ignorant Limey, whose vehicles still have pudding stirrers and clutches rather than this new fangled two pedal setup, I'll have to get round to getting some auto fluid to try it sometime. And compare it to GL4 or GL5 manual fluid.
The 'Merkins have another tool they call a red hot wrench - heat from a blowtorch to expand the fixing and crack the rusted joint. Very effective, especially if combined with a lubricant when hot (or the end of a candle).
American methods >>