Silicone-based lubricants, either oils or greases, would be ideal since they tend not to evaporate or dry out. Vegetable-based lubricants, such as olive oil, will lubricate well enough, but they gum up, dry out, and may even generate molds or other microflora--they're food products, not machinery products, you know.
You should be able to feel whether or not the nuts are moving in a nice, satisfying, lubricious manner, or whether abrasive, binding, metal-on-metal action is occuring. You'll see black film on the threads no matter what--it's going to happen.
Exotic, expensive lubricants aren't needed--we're not talking a gas turbine engine here. Lubriplate is a wonderful grease, petrolatum will work just fine, WD-40 spray will work (this is not a great place to use thin oils though), and so will just about anything else. If you used nothing at all, I doubt the drawbolts & nuts would wear out in your lifetime--but of course it's possible.
I wouldn't use a vegetable-based lubricant--they aren't even close to synthetics in terms of lubrication and lifetime, but who cares? There's certainly no harm. I suppose there's some advantage to one oil that can work for the drums, the hair, the salad, and for "personal" applications as well
Once a month, maximum, I'd think, unless you have no life at all. One drop, dropped down onto the threads at the top of the nut, just prior to tuning up, if you're using an oil. To me this is NOT a place to use oil--it makes no sense. Oil is for continuously moving parts. A tiny bit of petroleum jelly on the threads each time the heads are replaced would make the most sense to me. Another good reason to use synthetic heads.
Edited By Bongo Boy on Feb. 07 2002 at 03:53