gear delema... need advice

[jstarr]

i have an 05 6.0L F250 with a 4 inch exhast turbo back, aftermarket intake, SCT livewire 9600 programmer, 8 inch lift, and im running 40's. i am looking to re-gear the truck. the guy at the 4x4 store said he wouldnt re-gear the truck. im currently getting 9 mpg. i know if i re-gear the truck with 4;56 it would go pretty close back to stock as i could get. this is my daily driver. i know getting 15mpg is unrealistic. what gears should i run to help improve my MPG atleast back to 12 or 13. should i leave stock 3;73 or go 4;11 or 4;56..... please someone help. i would like to order gears in 2 days.

[atvrider93]

where do you do most of your driving? how heavy do you tow if at all?

[xjeeper]

I used to manage a 4x4 specialty shop that specialized in gear work, I would reccomend 4.88s or 5.13s, you want to go futher than just back to stock, because of the much higher rotating weight. especially with a 6.0 because of their higher rpm powerband. First get the rotations per mile for comparison because many 40" are not anywhere near 40" mounted on the truck, the loaded radious, or just drive them with the stock gears and a gps and do the math. 5.13 and an actual height of 38.5 raises you rpms10% above oem at any given speed (70mph is now 2200rpm verses 2000 stock) about right for the much heavier wheel/tire combo, and about the same as an f350 dually.

[jstarr]

i dont do any towing.. i mainly drive it to and from work and around town