ThanksIf you can only invest in one quench oil, use steels that it was designed for to get best results. As said above, Parks #50 for 10XX series, W1/W2 and 15n20. AAA for 80CrV2 and 52100.
If you keep making knives, you'll eventually want both oils, and in a decent amount. I'm in the process of getting a larger tank for my AAA, as I can only quench 2-3 blades of 80CrV2 at a time before it gets too warm and I start losing some hardness.