I use Supco Gidds turbine oil, it is non gumming and has no detergent. Would also second the no penetrating fluid advice. Most penetrating fluids contain a lot of solvent to dissolve grudge/rust and carry some type of oil as a lubricant to be left behind after the solvent evaporates. I have heard that WD40 contains some fish oil. Whatever is in it, the product does create a bit of of a rust barrier but after a few months it turns to a sticky brown goo.