Has anyone here used aftermarket K&N air filters?

[Gold Metal Flake]

4. X2 on the ScanGauge.

I use mine to help maintain a 30MPG average on my daily commute in my Focus.
As for the K&N, the difference between it and paper filters is the K&N impedes airflow less than paper. The reason for that is the K&N material is more open than paper. The oil you apply to the K&N is what traps dirt, only it does not do as good a job of capturing fine particulates as a paper filter. So with a K&N filter you will be pulling in more contaminates. For this reason I have not converted to a K&N on my daily drivers.

For me, the Scangauge taught me a different way of driving, especially how to use my momentum to best effect and averaging my speed. 27-28mpg went to 29-30 and then to 30-31 with the addition of Continental Pro-Contact tires (with Ecoplus technology!) That Ecoplus stuff is some good shit. OK, my post is turning out to be just a copy of Fumesucker's.

Purely city driving still kills my average. Nothing can be done about that cuz you're always having to accelerate from a standing start.

What kind of car do you have?

Hey, here is an MPG-only version of the ScanGauge. http://www.scangauge.com/products/scangaugee/