Years ago we picked up a barrel of a very heavy oil - the label said "Cold Forming Fluid" - at an auction. I don't have any idication of the manufacturer, butu it was great for tapping; the oil was so heavy that you could dab it on with a brush and not have to worry about the coolant lines blasting it off.
Anyway, that old barrel is about depleted and I'm looking for other ideas. I know that a few old-timers still like tapping with oil, and we find that it does seem to work better, at least in stainless. I just wondered what some of you were using.