k&n air filter [Archive] - Bimmerfest - BMW Forums

: k&n air filter

06-21-2012, 07:38 PM
looking at putting in a k&n air filter in my 2004 545i

will I notice a significant difference in performance, sound, or gas mileage, etc.?

if not, what is a relatively inexpensive part I could get to see some improvement?


06-21-2012, 07:41 PM
I noticed the car breathes a NOT easier - and maybe I imagined it, but it seems that it is easier revving with the K&N drop-in filter. As you said, it wasn't expensive and it does seem to make a small difference imo.

06-21-2012, 07:52 PM
+1 on my 550i- Much better revving, and better milage overall. Make sure to remove your carbon filter above it- this actually makes more of a difference, overall.

One catch is to make sure that you clean your MAF properly every oil change, to insure there is no K&N oil build-up on the hot film.