IAJack

My '13 XLT Screw 3.5 ecoboost has seemingly taken a dive in city mpg's. It has 62,000 miles, 275/65/18 E Wilpeaks (heavy tires), and a 1.5 front level with Billsteins. It has new plugs, new air filter, clean MAP sensors and I drilled the weep hole, and I run 87 non ethenol fuel in it. Is averaging 12.5 city MPG with short trips normal? On the hwy it will step up to 16-18 on longer trips. With the tire size I have not adjusted my speedometer and the mpg's are according to the display on the truck so perhaps the actual mpg calculation is better or worse? Anyone else seeing these kinda numbers?

Spiky

That's about right. Average 15 or so? I have a slightly different size P Wildpeak and it gave me about a full 1mpg hit. Your gear ratio could have an impact, if you have 3.31 the highway sounds low. But short trips on 30mph roads are killer.

Driftboater

If you upgraded tire size, night consider trying ForScan to change. There have been mixed results with 2014 and earlier trucks, or use a tuner etc. Might also consider resetting the PCM - - to clear out the adaptive learning etc as it may help with shift points with the larger tires etc.

2017ExecFx4

with larger tires you are under-reporting the miles driven and therefore calculating a lower than accurate MPG number. (Besides the on board comp is error prone)

Stu Cazzo

3.5 eco owners ( until recently that included me) like to hear the turbos spooling up - hence that causes lower mpg.
Try this - I know it sounds crazy but move your pedals back a bit - closer to the fire wall.
I found by doing so I was less likely to make hard accelerations and my gas mileage improved - more so as a result of how I was driving.

5.0nly

I'm averaging more than that in my 6.2L Limited.

Spiky

He said he's running stock size, just the weight is different.

IAJack

My stock tires were the Wranglers, I thought they were 265's?
the Falken's are quite a bit heavier
My gears are the 3.31
I reset the PCM when I changed plugs
I have read that Forscan cannot change the tire size on 13's
I am really light on the throttle and drive like a little old lady.
I suspec the with the heavier and largrWildpeak's that I am getting a little better than the computer is reporting. I will have to calculate my milage the old fasioned way on a couple of fill ups.

marshallr

That is stock size. Going to the heavier E rated tire will have absolutely no effect on fuel mileage. The more aggressive tread of the Wildpeaks could account for 1, maybe 2 mpg. Maybe none. Winter fuel WILL make 1-2 mpg difference.

My 14 with 5.0/3.55 gears will give me 14-15 mpg for my everyday driving on summer gas. About 18-19 hwy. Take 1-2 mpg off that with winter gas. I'd say your close to normal. Maybe a little worse, but depending on where you have to drive that may be as good as it's going to do.

IAJack

I moved to AZ so I do not know if they use winter blend fuels? It has been cooler here in the mornings (34F) so I have been starting my truck in the mornings and letting it warm up for about 10 minutes before work. My communte to work is less than 5 miles and the max speed is 50 for maybe a one mile stretch. I can live with the MPG but I was starting to wonder if is stuck in 4X4, or my truck was taking a crap or Eco's just do this with age?

In searching and reading the forums I am starting to beleive that this isn't too far off for a Eco with 3.31 gears.