I have never met a penetrating oil that works better than my propane torch. I have no time for soaking oils. If I'm doing an alignment and I have a seized tie rod, the first thing it gets is the torch. Exhaust flange nuts? Torch. Once it breaks loose, then I skeet some WD40 on the threads for some temporary lubrication.
WD40 is the only spray can that I keep on my tool cart. It's nothing magicial. I like the smell, it's safe on most surfaces, the flippy straw nozzle is cool, and it has multiple uses.