I have an OEM style AFE proguard 7, cleanable, oiled filter. I have always used the cleaning spray AFE sells. The last trip up to the AZ high country I made I noticed a distinct lack of power and could hear a funny noise. I thought maybe I had a ripped air intake piping rubber boot. When I got home I inspected the filter and man it was just dirty. I put a couple of gallons of hot water and some simple green in my deep sink and washed that filter until I no longer got dirty water out of it. Man is it clean now. I let it dry thouroughly, oiled it and installed. Truck runs great. I am a bit embarrassed I let it get lke that, but honestly, I used AFE's cleaner and thought all was OK. Boy was I wrong. Just thought I would pass on what I learned.