Aldo said the filter is felt, Deejay. Felt tends to be rather dense. I have trouble imagining getting air through felt that was soaked in oil and dripping. My preferred theory is that the oil was a tenant's improvement, at least in quantity, but probably in being there at all. There is a picture of the felt in the owner manual, but I can't seem to post pictures in this forum.
I agree that Honda foam pre-filters need to be oiled to be effective. The ones I have are only a few millimetres thick, and quite open. They wouldn't do much at all without oil. With oil, they keep the oiled paper secondary filters remarkably clean. Incidentally the foam filter on one of my Hondas was dry when I bought the mower, and I've seen instructions somewhere telling people to use them that way.
