I was getting around 15.25-15.5 MPG w/ 37's and 4.88's.

Last week I added a K&N drop in and this tank I got 16.67. Not sure if it's significant or not. I'll have to run a couple more tanks through to get an average.

Most of my driving is below 60 MPH though. If you travel the Interstate (70-80 MPH), your fuel economy will plummet (or at least mine does).

 

I was thinking that on the highway you should actually gain mileage (if you're traveling at normal highway speeds ). Theory being "IF" you're on flat highway the lower RPM's should conserve fuel. Kind of like overdrive...lol Now this is based on my 35's with stock 4.10 gears and automatic tranny. Now around town (stop and go) it takes more power to move the vehicle so the gas mileage drops.

 

Cool.......Thanks for the input you guys...!!!