I normaly use about a gallong for most sizes, but my quench is set up as portable, when I get my shop built I plan on a permanat tank set-up with about 3-4 gallons. I also normaly only quench 1-2 blades at a time so a small quantity of oil does me fine. If I was quenching a bunch of knives I'd need a lot more oil to keep the temp down.