Be careful what you use, and think twice about storing your prize in its leather sheath. ( I assume you are speaking of leather, since nylon/Kydex/Concealex etc, need no preservatives. )
As my knives go through rotation of being used or new favorites, my old Brownings and Shrades suffered a lot of corrosion on the brass hilts and guards. Even the pins turned green a grew fungus on the Browning that I kept in the leather sheath. Granted, the Browning was in the sheath for a couple of years, but I was surprised nonetheless.
On my hard use knives that have leather sheaths, I use the same thing I do on my winter hiking boots - Sno Proof. On my knives with less robust sheaths, I have used Fiebling's Neatsfoot oil with great success.
I have an old Buck 119 that I have had since I bought it in '73. It has camped, canoed, hiked, hunted and generally been taken for granted since I bought it then as my go to knife. I have the original sheath of the foldover holster style and it is still in great shape. It has a liberal slather of Neatsfoot oil when I think about it and it is as supple as it ever was.
I don't store knives in leather sheaths anymore. Unless the sheath is dried out to the point of being cardboard, it seems to corrode the fittings on all my knives and their blades (if they are carbon).
Robert
