2017 F350 DRW 6.7 4x4 with 4.10's and 22k miles - I'm seeing 17-18 at 68mph on flat ground.

 

 

I usually get in the low 17's running the speed limit...you'll probably get the best if you can keep it down to 1700 rpm's which is around 65mph. I live in the country and running around town I usually get 15 to 16 mpg so I find the 4.10's accelerate the truck easily and help the fuel mileage. The fuel mileage is better then I expected on such a heavy truck.

 

i have yet to really get a full tank unloaded and will probably never happen especially all highway. averaging 13 this tank and that was with a very light tow and a bunch of around town.

 

 

 

Crewcab, long bed. That is per the computer.

 

 

Computer lies.
I always do hand calculated.
I also calculate the difference between the computer and hand calculated.
I see a difference of .6-1.1 MPG.
In the bad direction of course.

I got 3.55's in my '19.
I was hoping for better unloaded mileage than I got in my '12 with 3.73 gears.

 

Should be doable. My 450 with 4.30s shows 15.5 to 16 at 70-72.

 

I will never go to the 3.55's, I love the 4.10's. I tow over 20k regularly and can't imagine life without them.

 

 

 

Picked up my '19 F350 SRW 3.55 geared 6.7L with 50 miles on the odometer last weekend and immediately drove it 1000 miles from Philly to Iowa. Dash computer showed 17.8 mpg on the drive. Cruise control was set to 79 mph for most of the drive through the midwest with a little bit of higher speed passing and slower speeds around construction areas and outside larger cities along the drive. I was under the impression that fuel economy improves a little bit as the 6.7L breaks in but it sounds like that may not be the case based on what I am hearing in this thread.

I did notice the one tank of B20 I had to put in the tank in Indiana seemed to net me an extra ~1-2 mpg than regular diesel.