Hello all I have an 07 F150 CrewCab 4x4 5.4.. With a 6" Lift Sct
custom tunes, Magna Tru Duals, 35x12.50r17LT cooper discoverer, 3.73 gears, Only getting around10 mpgs.. Was wondering if changing my rearend gears would up my mpgs much and what would be the best option..Dont do much pulling just basically just normal around town driving.. thanks hopefully I didnt leave out any needed info...

 

The lift and tires are killing your mpg's. Have you heard the saying you can't have your cake and eat it to? Do you have your computer reprogrammed to account for the bigger tires? If not then you are off on your mpg calculation. The only reason to change the gearing is if you lost a lot of takeoff or low end grunt. But if you aren't towing you probably don't need to change.

 

Something else seems amiss here. Even with the lift and 35's, 3.73's are a descent all around ratio to have. 10 mpg seems low even for your set up. Gears can absolutely make a difference in fuel mileage, but not exuberant; maybe 1-2 across the board.

 

Yes I have reprogramed for larger tires so mpg is accurate..And I realized my mpgs would be lower with lift and tires just didnt know it would be this low.. I bought the truck already lifted, and after I bought it I changed plugs and coil on plugs had problems with new plugs burnig the electrode off the top of like 5 plugs using the reccomended SP515 plug I believe thats the correct number any how after wondering why this was happening and Ford or no one else had a clue noticed the plugs I pulled out where SP514 because I wasnt sure if it wasthe COP's or the plugs causing the problem I but the old plugs backin ran fine so I bought new SP514's and havent had a problem since except maybe low mpg's..

 

I would discuss the low mileage and the spark plug issues with your tuner. SP514's are for the 4.6 3v in the Mustang.

 

I have a 2005 with a 6 inch lift 35's and 3:73 gears. I have a superchips tuner
and average around 12.5 to 13 mpg. I am in the process of going to 4:56 gears.
Mostly because I will be towing and I feel the engine does need a little help. I am in the research part right now. Probably yukon gears, detroit trutrac in rear.

 

It had the sp514's in it even before it had the tuner back when it was stock..So I just assume the previous owner had a problem too.. But I dont know it was weird..

 

4.56's should improve your city mpg. Might slightly improve the highway mpg as well due to the motor not having to work as hard. I would not expect much though.