bgautreau

Guys I need some advice. I am a new owner of a 2015 XLT w/ 2.7 Ecoboost. I drive approximately 30k miles a year, 99% hwy. I've had my truck for approximately 2 weeks and averaged (computer calc) 24 mpg here in Louisiana. This is a vast improvement over my 2006 4x4 Lariat that averaged about 16 on the hwy. I wasn't crazy about the 18" wheels and stock tires so this weekend I had them replaced with 20x9 Fuel Throttle rims with 295/60/r20 Nitto Terra Grappler tires and a 2" level kit. The truck looks great but my concern is with the computer millage that I am now seeing. I took it out for a 20 mile trip on the interstate and noticed that my instant mileage was down to about 16 mpg at the same cruising speed that I experienced 24 mpg with the stock tire/rim combo. The truck has not been aligned and the speedometer has not been calibrated yet. I'm curious as to what other are experiencing with a similar setup. Please help as I am now considering swapping back to the stock setup! I'm willing to sacrifice 3-4 mpg for looks but not 8.

JayS2015

Same thing happened to me - and i posted about this earlier tonight looking for advice.. I have a 2015 Lariat 2.7 that came with 265/60/18.. looked RIDICULOUS.. found on Craigslist someone selling the 20" chrome wheels/tires off a lariat also 275/55/20... So my speedometer is off also and gas mileage tanked too.. but that's because the computer is not reading your accurate speed - your size is even bigger, so will be even more inaccurate. Revs per mile on old tires were 660 - new set up is only 630..

But what you're seeing on the computer is not at ALL what you're really getting with MPG.. It MAY hit you by 1 or 2 MPG -

JayS2015

The lift may also take another 2MPG or so off - but you shouldn't lose 10MPG with all that... tire size will less effect MPG than lifting up the truck changing the aerodynamics..

bgautreau

I did some digging and was able to decipher that the stock tire/wheel setup weights about 64 lbs. The new tire/wheel setup weighs about 105 lbs. That's a bid difference in weight. I have no experience with this so I wasn't sure if that translated into a substantial difference in mpg. Thanks!

JayS2015

yeah, tons of added unsprung weight will impact MPG.. combine that with lift, larger tires etc... it will definitely impact... but your MPG readings are not at all accurate.. you probably changed your tire diameter by 2 or 3 inches will completely give you false readings..

130428

to get an idea of how much your speedo / mileage is off:
http://www.rimsntires.com/specspro.jsp

XLT_AK

So is it possible to recalibrate or not?

JayS2015

no - Ford said you cannot re calibrate speedometer on the 2015

A-West

Is it not possible to change tire size with a flash tuner

PawPaw

Running that many miles a year the tires and the leveling kit will eat you up on the highway. The last couple of trucks I had lost about 2 to 3 mpg's on the highway as opposed to the stock numbers. I felt I could live with that because the looks were so much better then the stock look. I did a compromise on my '13 and only leveled 1-1/2 inches and went with one size up P rated lightweight Toyo's. I still can get up to 20 mpg's on the highway under ideal conditions while still retaining performance and braking when towing. Once you get the speedometer corrected you should only find a 3 to 4 mpg drop at the max.