Dave, take a close look at the filter media, maybe with a magnifying
glass. If the media is relatively thick, with random fibers going in all
directions, then the filter requires no oil.
An oiled type media is usually made of cotton gauze, and is woven in a
symetrical pattern and is thinner. You can actually see through the fibers
on some, specifically the K&N.
I've been using the (washable) Fram Synwash filter in mine, which is a no-oil
type media. I like the convenience of no oiling, plus the peace of mind about
possible MAF sensor contamination with the oiled filters.....