If you mean put away and forgotten for years then you'll need to wipe clean, dry, oil and wrap in oil-cloth. Any non-acid content oil really. If you mean, wiped, put in the sheath then taken out again a week later - literally I wipe with any machine oil (3:1 is fine) damped cloth and sheath it; my sheaths end up slightly oily inside (which I think is good). I always wipe my blades down before using them on food. I once had a sheath that started smelling a bit rancid and I presumed it was the vegetable oil I had used so stopped using it - but that was a very long time ago and I could have been wrong.