With my 8700 lb 2013 F350 DRW 2x4 4.30 gears running stock 245/75/17 tires I average 11.5 to 12.5 in town, it really makes a difference on which town I'm in and that's always overlooked when comparing mileage. Jackrabbit starts also make a difference but the biggest difference maker is the number of traffic signals and traffic, also the posted speed limit is just that, doesn't mean you have to drive that fast in town or out on the road.

Denny

 

I will defer to Denny's request here.

But you have a lot of growing up to do little man.

 

Ok the very first thing I would do is use a standalone GPS and check your speed at 60 mph and see if it's been corrected for the bigger tires. Next the simple stuff like jacking up the wheels to make sure the brakes or anything else is dragging in the drive line, change to a top tier gas and run a tank through it, I never believed in the gas until last fall (long story). Next look at your tires because you are running 12.5 wide meats, instance mileage killers just like the ones on my F150, raise the air pressure to the max but it will ride harder for now but you will know if it makes a difference.

Just a guess but I'm thinking your speedo was never set to the bigger tires and the 12.5 in tires are killing you. Do the simple things first before spending $ on it. The electronics on the 6.2 are great but in some cases to good because you can't tell if you got a bad load of gas, it adjusts for it and the only way you can tell is the mileage.

Denny

 

Apparently you do since you aren't mature enough to hold a decent conversation without being offended, and resorting to personal insults.

 

If you can't add anything useful to the OP problem in this thread don't post, first and last warning.

Denny

 

I have a ccsb on 37's with 4.88 gears. I average 10+ mpg on my daily drive which consist of 12 red lights in 9 miles. I can pretty easily average 11 if I drive conservative. The large 20" factory wheels come with a tire measuring 34.1". Your 35's are probably only about 34 1/2, so not much difference. The big difference is the width and weight.

 

Put 800 miles on my truck since I purchased it. To date the trip computer tells me the overall average is 14.1. I havent towed anything with it yet and most of my driving is 55-65 with about 25% around town.

 

Hand calculated is the only way to get your true fuel mileage, the computer is often inaccurate, that's why it's nicknamed the Lieometer.

 

With mine if I keep it under 65 when not towing it will get that kind of mileage but go to 70 and it's downhill from there. just to much wins resistance and in my case low gearing.
Denny

 

Thanks so much. I will try that. Yea Im not even fond of the looks of the 12.5. Too wide for my tastes. Once I need new ones I will go back to the OEM size.

I appreciate the replies. This board is amazing. Thanks everyone

 

The best methods I found for improving fuel mileage are:
Always anticipate the stops or slow downs. Coast whenever possible when traffic will permit it. Anytime you press on the brakes you are wasting fuel.
Never use the cruise going up or down steep or long hills.
Try to find the happy medium between best mpg's and highway speeds. We all like to get there faster but it costs. On the highway I stay at 65 (speed limit 70). I am sure 60 would be even better but its just not for me. Going down hill I will often coast till I am 5 over the speed limit before hitting the brakes then will stay off the gas until I coast back to 65.

It really does help.

Finally, when we go on longer road trips we take the Civic and enjoy 35-42 mpg running 70-75.

 

I do both hand and meter checks, and have found my MPG values to be quite accurate between both methods. Typically dead-nuts on, or only 1/10th of MPG shy.
If my truck is lying, it's only a tiny little fib every once in a while.

The value of the MPG reading and it's accuracy is a function of many things; several inputs go into the formulas for the vehicle read-out. Apparently I just happen to get a truck where all the sensors are spot-on accurate. The normal allowable design and production variations will induce some amount of error, typically. I just must have gotten lucky where all my components are right on the mark with almost no variation from print spec.

 

I am seeing about the same disappointing MPG in city driving and hilly country. There is little doubt that the unsprung weight difference on those BIG tires are going to cost MPG but switching to stock is expensive and I do not believe you are going to get the kind of increase you are looking for. Say for arguments sake...you get 10 mpg over 500 miles equals 50 gallons. You switch to stock tires and voila 12.5 mpg! Over 500 miles equals 40 gallons. Next, 4 tires at 290 each=$1,160.00 10 gallon savings on fuel times pump price say $2.50 a gall equals $25.00 off set in savings. Now 1,160 divided by $25=46.4 times 500 miles = 23,200 miles to recoup your out lay on tires. I suspect with rims figured in it may take longer and at greater cost.
So this comes down to a few questions to ask your self. Will you keep driving this truck that long to recoup the expense in fuel for the outlay for switching tires? AND will you see a 2.5 mpg gain? My fuel mileage is miserable after switching from my 1999 7.3 diesel. Took me forever to get over the dismal difference. The cost of diesel...and DEF plus the outlay for upgrading to a diesel engine, simply was not worth the cost for my kind of truck usage. I love ford Super duty crew cabs so 6.2 it is.
My advice friend is give it time and learn to accept the cost of ownership of a true THIRSTY friend. Took me almost 2 years now to become fond of this truck over my diesel. I do enjoy the cheap oil changes, not smelling a bus, hard cold starts...etc
I read everyone's posts and they are advising you well. I have seen some outrageous MPG figures thrown around on this site. I have 3.73 locking rear. I can not see any advantages in changing a rear ratio for allegedly better MPG's. Your driving habits, your home turf, quality of fuel, these are going to affect your MPG's more than anything else in my opinion. So in summary...maybe save the money you were thinking of spending on refitting and use it at the pump. Accept the thirsty friend who's bar tab your constantly picking up. Come to think of it...I have a brother like that! I bought my 2016 new and after about 23,000 miles now i see 10.5 stop and go city...15 highway at 65-70. I just towed a 20 foot travel trailer from Delaware to NJ and saw 10.3 on the highway coming back....14.3 going down to get it. This is typical mpg for me.
Good luck in what you decide. This is a great forum for information and everyone seems to give sincere honest input....except those MPG guys....lol Some...not all...some are getting out and pushing!

 

My best MPG has been around 15.5mpg for all highway at a steady 70mph cruise, unloaded.
My "daily" mileage is around 13mpg, mostly highway (70%) and city (20%) with the last 10% a mix of idling, warm-up, etc. It's fairly flat where I'm at, with the exception of my neighborhood which is quite steep.
Anyone getting 11mpg in hilly areas and stop.go driving is probably doing about as well as can be expected.
Anyone stating they get 17 or 18mpg is only looking at the display when they're heading downhill ... with a tailwind.

 

You can correct the Liemeter to be pretty accurate using the info in this thread: https://www.ford-trucks.com/forums/1...l#post18092841