Quote:
Originally Posted by mlifxs
I did the K&N and charcoal delete on my 328i.
Could be placebo, but I did think my car felt a little stronger after the change. Again, could be wishful thinking 
One thing, to this day, that is not placebo is the 1.5 hwy mpg improvement I now enjoy after the change.  |
So how do you exactly know you have improved 1.5 MPG on the highway? How have you tracked just your highway mileage MPG?
I keep exact records of all my cars MPG using a book and recording the miles driven and gallons for a complete fill up for every tank of gas (I completely fill the tank every time). I never saw any long term increase in overall average MPG in any car I used a K&N filter in.
There is no benefit to using a K&N. If a manufacturer could magically gain 1.5 MPG (and horsepower) on the highway rating for its cars using a less restrictive filter, it would use that filter as a production part and would make the cleaning of the filter as part of the scheduled maintenance program; especially BMW, which get constantly fined for not meeting U.S. CAFE requirements.