Oil is always safe for quenching, I believe. Its never failed for me or my friend, we have been doing this together for a couple years now. Vegetable oil, motor oil, doesnt matter. any oil.
Also, be very careful of it flashing up, it can burn your hand or arm, and never lean over it, heh. If it does, dont worry, just completely submerge it and the flame should die out in seconds. Also, use a LARGE container, at least a 2-gallon bucket, thats what I use, no problems. As always, use my advice at your own discretion.
