Genius! I have wondered about oil too, but didn't consider something like tuna oil! That would certainly be a brilliant method to keep your tools in shape.Still you can't use plastic bone cutter or scalpels, etc. Just something we have to live with.
I have a bottle of tuna oil I got from a fishing outlet, it's used in making berley and costs about $6. A good rinse and dry after use, a quick spray with oil then I wipe as much as I can off with paper towel. It seems to work, I've had one of my two scalpels for about 12 years.
Being fish oil there is no worry about harmful residue and there is almost no smell once it's wiped off and allowed to dry.
I think these would make an impressive gift for any fragger.