Yes, I value Jet's opinion (I have used his "spring helpers", poor mans ladder bars quite effectively). However, even a good AD filter will not pre-pressurize the oiling system and it still takes time for oil to move through the passages upon startup. Of all things we do to our engines, I think one can easily argue that startup is the most detrimental. I've read while doing research that 50% of an engines wear occurs at startup (something like 7000+ cycles on an avg engine). Do you agree? Many piston engine aircraft use them, as well as many racing engines (pre-oilers have an added benefit that they provide a reserve of oil in case of momentary loss of oil pressure). I would love to have some emperical evidence showing a significant reduction in engine wear over many years. But alas, I probably ask too much. Oh well, like you said, what's a couple hundred bucks for some piece of mind.