That's a good question. I don't know the "right" answer, but for me, it depends on what I'm using the knife for. For general finish and protecting against oxidation, I use a wax. You can use Renaissance Wax a good car finish like Meguires or Mothers. I use a mold release wax that's very tough. I also use a few drops of light machine oil after cleaning a dirty knife, or if it's something I use for food, olive oil.
Hmmm...on a carbon a high carbon blade I believe a little bit of any light oil will do the trick and stop any rusting.
It will depend on what the knife is used for, but on a knife that is intended for anything other than dedicated food prep, renwax seems to be the go to stuff. I have used vegetable oil, mineral oil, and even boiled linseed oil on hawks and axes. WD40 will also work on knives not intended for food. Another tip I heard yesterday is for knives you are working on or tools in humid conditions. I have been told a shot of dykem will help prevent rust while storing blanks, files etc.
