Make sure you're not setting off on a wild goose chase. Are you absolutely certain it's oil you're seeing? Could easily be gasoline residue, which looks and feels a great deal like oil. Are you actually losing (using) oil as indicated by the dipstick?
You may want to just put an oil trap in the PCV hose between the valve and the intake, either to keep the oil out of the intake tract (if in fact it's getting there by that route) or at least to see for yourself what amount of oil is travelling along the PCV tract. It's not hard to make an oil trap or you can adapt an oil separator meant for use on compressed air lines. See here, here, here, and here. I would use the copper or stainless scouring pads, not the plastic ones.
