bmcmarshall85

I have a 2015 F-150, 3.5L V6 Ecoboost, 4x4...I just changed the stock wheels and tires to a 20" rim, and 33x12.50R20LT tire. I have noticed a 2 - 2 1/2 mpg difference. Also, I am noticing the speed-o off by about 3-5 mph. Is this something a tuner can help with. I did jump the gun and get the SCT X4 tuner. Does anyone have this tuner? Is it good? Does it come with preloaded tunes? In short...did I screw my truck up?


Brax

tuflehundon

SCT4 is a good tuner. It can help you correct your speedo for the larger tires. Getting custom tunes from MPT, 5 Star, or one of the others will be much better than the stock tunes that come with the tuner.

bmcmarshall85

So I didnt screw anything up?

sierrafast

No.. Just use the speedo calibration feature on your X4 to calibrate for bigger tires. The decrease in the mpg is due to the heavier wheel tire combo and also you effectively changed your gear ratio with the larger diameter tires.

gocolts09

5 Star can fix your speedo and give you more power, mileage, and better drivability. There are websites you can go to that will tell you what the revs per mile are on your tires so you can put the input in the tuner

Scott91370

You're not going to be able to tell how much of a mpg difference you have until,you get the speedo calibrated.

Z7What

As it was said no you didnt screw anything up. The MPGs dropped for two reason. The heavier wheels and tires and because your speedo is off. The truck is traveling further than what the truck thinks it is so the MPGs are off.


The SCT X4 is a great device. I would suggest not even wasting your time with the preloaded tunes. Get a custom tune! As for who to use, i would suggest Torrie @ Unleashed Tuning but you do your own research and decide.


Wayne