Gearheadguru

So i have a RCSB silverado with a 4.8 and an open diff wrapped in 3.23 gears. the stock tires are 245/70/16 which are 29 inches high. (with no weight on them) i am currently running 265/70/17 (31.8 inches high with no weight on them.). I am going to be swapping to a eaton posi wrapped in 3.73's and a nelson tune. I was wondering if i would still be at about 20 MPG on the freeway because of my tire size and what kind of gains i can expect from the trio. I would imagine my city MPG would increase slightly?

P.S. Anyone have anything bad to say about a nelson tune? I cant find anything to deter me.

Whitecrewcab

iTrader: (2)

My 06 CC has 22" wheels, cam, tune, full exhaust and 3.73's. I get 19+ mpg on the highway at 70-75mph. A regular cab should get even better.

Mud slinger

iTrader: (2)

What kind of terrain do you live in? If it has hills and what not then I'm sure your mpg will stay around the same, if not improve. Extremely flat I don't see an improvement on just hwy mpg, but shouldn't notice a drop either.
Nelson is highly recommended around here.

TXSZ66AVLANCHE

iTrader: (7)

With my RCSB 4.8 I didnt get anywhere close to 20mpg

SloStepSide

iTrader: (8)

Pshhhh, I don't think my saw 20 mpg before modding. Lol

DTHPROOF

iTrader: (1)

When my truck was 100% stock (5.3), I got 420 miles per tank like clockwork. Every tank for over a year. I think that's pretty good, and that's with factory 3.73's and a 30.5" tire. I'm getting a valutrac in a couple of months and I'm still debating changing the 3.73's out for 4.10's. I just don't want to waste my money and not feel any difference. I think you'll be the same or better O.P.