Does anyone know of any mods that really work for better gas mileage? Chips? Ive heard of something called a flowblade off of ebay that supposedly increases mpg. Im lookin to fit 38s on a 7 inch lift, and just wanna know what type of gas mileage im going to have. I have a buddy who runs 38s on his sierra and he gets 18 average.

Unless you start getting into physics and start recalculating air drag, wind resistant, tire reistance (of course the tread makes the biggest difference when you get a lift), added weight, etc. I think you're going to have a hard time figuring out ahead of time what you're going to be getting.

If you want to keep you MPG to a maximum, keep your rolling resistance to a minimum (i.e.: A/T's instead of full off-road tread), and get your motor to have the most efficency it can have. Better breathing (in and out), keep it properly tuned, etc.