Just bought a cheap filter at auto zone for 7 dollars just to get the car on the road because the weather was nice and my 40 dollar filter didn't come in the mail yet. I took a round trip for 150 miles and averaged 31.5 on the way there and maybe 30.6 on the way back and it was very hilly. About .5 MPG increase. Not as good as I thought it would be, can't wait to get the new one in which is K&N!