Here is what I have as far as TEST DATA on K&N's. Nevermind the slick advertising and promotions and scores of users who have never TESTED them.
We have two diesel trucks and heard how much better the K&N's flow. We bought two and put one in each truck. In the course of 6 months the oil analysis ( http://www.blackstone-labs.com/ ) showed the silicon level in the used oil jumped from a baseline of 4-5 PPM ( 9 PPM is max allowed ) to 35PPM in each truck. Silicon is the amount of dirt/sand in the oil. Dirt/sand in the oil = BAD.
We switched back to OEM air filters and the silicon level came back to 5PPM on the next change. We always monitor the oil condition after a change to the engine, injectors, fueling etc.
Others in the truck group have noticed the same results.
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