TheRok

I have seen this question asked in other forums but could not find one directly in W209. If there is, my apologies.

Has anyone changed their air filter to a K&N? I have received mixed reviews that it helped with better gas mileage to it killed their car. The part is less then $100 dollars and seems like a cheap improvement to the car. On the other hand I don’t want the sensor to get clogged or dirt to get into the engine.

Please advise your experience with aftermarket K&N air filters and discuss any issues you may have had or good experiences.

BrabusClK04

I have it on my car. Didnt feel much gain. I replaced my filter when i changed my exhaust system. It might of helped a little, but not alot.

Fluid

Flow testing of clean paper air filters vs clean K+N filters doesn't show much difference in pressure drop ( resistance to flow ), but testing between dirty paper filters and dirty (or clean) K&N filters shows much less pressure drop with the K&N. If you replace your paper filter regularly you will not see a real difference with the K&N. If you only replace your paper filter every two years, then the dirty K&N will flow better after two years and you likely will see a difference. Some have reported engine damage from the K&N allowing more abrasive particles to pass through ( it does not "filter" quite as well as good paper ), but I've used K&N cone filters for years without complaint. But I don't ket mine get too filthy either.

Carbon9

K&N "might" give you a wee bit more but they do not filter quite as well.

I doubt you would be able to feel or see any difference (gas mileage), just by dropping in a set of K&N's.

For everyday street use use what's already there.