They have tests where they pass dust through them and then weigh the filters afterward. The more the filter weighs after - the more it stopped. The less it weighs after - the more dirt went into your engine....
K & N loses big time to any alternative - paper, foam, whatever... On road or off road - doesn't matter. On road you get the other common problem happening - the oil on the filter media is pulled through and "fouls the MAF" - the mass airflow sensor (maf) becomes fouled with oil and doesn't get a good reading.
And given the media they will typically clog much, much faster in extremely dusty conditions when compared to a multi layer foam filter..
My advice - and I will be blunt.....
Throw it in the trash or sell it to someone you really don't like....
Friends don't let friends use a K & N....
jeff
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