Oil on water is OK enough on some 10XX steels, most other carbon steels need oil. For the best results, there are specific oil quench mediums for specific types of steel, but they are costly. In most cases the right oil negates the use of water at all. NO. Used motor oil is a very poor quench oil. New motor oil is hardly better. If you are not wanting to use a formulated quench oil, you can get by with using vege cooking oils, and for some steels, mineral oil. All of these oils do best if heated to around 125/130°f. Hot oil quenches better and faster than cold or ambient. 01 steel can be quenched well enough in mineral oil, and pretty good in ATF. 1095 needs a very fast cooling quench, and will do pretty well in canola oil. Tests have shown canola oil to be the fastest quench of all the vegetable oils. For 1095 strikers use warm brine. One common box of salt makes two gallons of brine. Brine quenching is paradoxical in cooling action. It cools faster than just water, but salt greatly reduces the chances of cracking the steel. Uneven cooling is the greatest cause of cracked steel in a so called water quench. Red hot steel going into water instantly forms a surrounding of the steel of a vapored steam, that prevents even contact of the water with the steel. Steel going into brine is instantly covered/coated by the salt. The salt prevents or reduces the vapor jacket/bubble around the steel object that plain water causes that prevents even contact with the water. As far as hardening a frizzen, the oil/water trick is obviously useful, but warmed canola oil would give you about the same hardness as the oil/water with even lesser risk of cracking. A triple reducing heat cycling would reduce the risk even more yet. 1st cycle at bright orange. Let cool to ambient. 2nd cycle at a red heat. Let cool to ambient. 3rd cycle at a low red and still non-magnetic. let cool to ambient. Your piece will now have a velvet smooth grain size and be stronger. Now you can do your hardening process and have a stronger frizzen. This heat cycling is especially beneficial for cast steel parts.
For any of you using 1095 steel for knives, you have but two choices of oil quenches. Best choice, formulated commercial quench oil, such as Parks #50, or canola oil. For the adventurous, leave your edge a little thick and brine quench. Brine is the only quench that brings 1095 to it's maximum hardness. Temper as soon as you can handle it with bare hands.