Wintergreen oil (methyl salicylate) is the most penetrating of all penetrating oils. It is available at most drugstores at minimal cost. If you work on old machinery that is anywhere near saltwater (or salted highways) it’s an essential weapon in tackling otherwise hopelessly rusted/frozen threads. It smells good, and though toxic and not to be kept within reach of children, is intended for topical application to human skin.
— George Dyson
Many’s the time I could have used this. The nice smell is a bonus.