What is the overall opinion of the value of aftermarket (K&N, aFe) air cleaner elements? I'm speaking primarily of just the element replacement, not the airbox kits. I live in a fairly dust environment, so I like to keep a clean element in the car.
Air filters I have always used aftermarket filters and have not had any associated problems to my knowledge.
My M3 friends seem to like Streamline filters. Am unsure who makes the cone-type filter in my Dinan intake though. Biggest problem I hear with the oiled filters is over-oiling them and fouling the MAF. Take care with that issue and I've heard no other problems.
Several years ago, a member of a Honda motorcycle forum (I think VFR Forum) did a somewhat scientific analysis and had motor oil samples analyzed by a laboratory from the same engine after running with the stock paper filter and a K&N filter. The oil from the K&N filter sample had a much larger number of particles that represented contamination and the average size of these particles was larger than the oil sample from the paper filter test mileage. The size and quantity of the contamination was not of the order of magnitude that would ruin an engine right away but it was enough to cause concern if you keep your car or motorcycle a long time and run the engine well over 100K miles. I am not trying to single out K&N. I think their product is representative of most other 'high flow' filter elements. Bottom line is that their filter will pass particles that the OEM filter will stop and this could be a concern if you drive your car a lot on the street and intend to keep it a long time. My cars and motorcycles are keepers and I still use OEM paper filters. I don't think this should be an issue with track cars or garage queens that only come out on nice weekends. It has been at least 7 years since I read this information and I do not remember the specifics any longer. I offer it as a caution to those who value long life over the typically modest performance gains you get with aftermarket filters. If you doubt what I posted, at least do a little research on your own. I will see if I can find the original post I am referring to.
Hold a K&N up to the light - see those bright spots? Those are gaps in the filter medium - do you wonder if dirt will pass thru them? I have no doubt & use OEM paper.
