Originally Posted by sourbeer
I used an SCT livewire tuner with custom tunes and it did have the tire size setting in the tuner. It was a 2010 Ford F350 6.4L diesel and was a monster. My odometer still was off. The fuel calculator was WAY off with the tune.
I'm also wondering, if you change your gearing, tire size etc... how far off is your fuel calculator that you are showing in your picture. I can't imagine that is accurate. I have a hard time believing that you can get 14-15 mpg with a lifted truck with 37" tires when my factory truck with 32" tires and 3.92 gears is getting on average 15. It is new and I know mileage will get a little better, along with driving style for some but I think there is somehting off with the mileage calculation. I would love to think that I could add big tires and not hurt my actual mileage that much, but realistically I think I am looking at a couple mpg atleast by going to 35-12.50 tires.
Not sure why you would think the od and gas mpg would be off. You correct it by changing the tire size with a either a tuner or in my case a Hypertech Speedometer/odmeter calibrator. This technology has been out for a while....kinda blows my mind you couldnt change it on a 2010 Ferd. Sounds like you had a case of operator error
That hypertech corrected my speedo/odo for the tire change and also changed my programming for my 4.56 gears. for the shift patterns and what not. So yes EVERYTHING is correct and have even verified by GPS and done mpg hand calculations....
You will lose a couple mpg with stock gears and going to 35s for sure. With 35s you're geffective ratio will be about 3.55 with heavy ass tires. With my 4.56s my gearing is still quite a bit lower than yours in stock form, I'm right below 4.10s with the 37s. My in town mpg is a beast, however hwy is my worst bc of the rpms I run going 70-75mph.
You really dont have to belive me, Im pretty sure my picture is enough proof.