Import, not contesting what you looked up and derived from it. My original source is a well known 30 yr Cummins Engineer who was involved in significant heavy equipment testing using historical oil analysis from scheduled PM on a fleet of equipment having run the oem micron spec filters. K&N asked the customer if they could demonstrate a cost savings on the fleet by use of washable filters. They did save considerable money on the filters. but the oil analysis went to **** with substantially more dirt in it drastically changing the oil change interval and erasing any savings.
This is not urban legend, spoke to the horses mouth. It's become well known in the offroad and diesel truck world.
NOW that was ten yrs ago and if K&N was smart they would have altered their product to perform more admirably. Maybe they have. It's simpler for me just to verify oem micron ratings regardless of brand.
all that said, sleds and boats don't even use air filters. Most of us spoiling our cars don't see a lot of dirt roads, but, it used to be relevant..... and me still be relevant for some.... so i shared, eyes wide open. Forgive the hijack.... motor on
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2009 silver sport, 6MT touring and nav, 8700 miles when I got it, "almost" a daily driver now... bone stock aside from tint and Gemini CBE, PC'd Rays black stardust and running 275/295 DWS rubber