if this has already been done to death I apologize. I did do a search and didnt see anything. So here goes. Has anyone compared mileage figures running a k&n replacement filter only, vs installing a complete fipk? I've been looking at the intake on my 5.4 and it seems to have pretty big tube diameter stock.
last time I priced a fipk it was almost $500. That was for a Grand Cherokee.

 

Moved to proper forum.

 

ok, I found an earlier thread, this has been beaten to death and a lot of people got ugly over it, so disregard my query.

 

Some people do get "religious" about the use of K&N filters, but your specific question has a relatively easy answer.

For any filter to increase mileage, it would have to present a significant reduction in the air flow loses compared to the stock filter at normal cruising RPM's (NOT at peak horsepower levels). There is debate as to whether either of the K&N setups increases flow significantly at high RPM (high horsepower, high flow) compared to the well designed factory set up on a stock engine. However, even if they are slightly better there, it seems unlikely that this could make any difference at cruising RPM's.

I know many claim that they do get improved mileage, but I think it must be when compared to a dirty filter and/or on an older vehicle.

 

well there was enough negative 'evidence' presented to make me question the worthwhileness of installing a K&N setup of either flavour. Usually I run Fram but I get the impression someone has come up with arguments agains them also.