I have a 2011 f350 6.7 dually with 190k, bought it with 180k. Truck is tuned and deleted. Since I bought it, it only gets 11-12.5mpg empty with the cruise set at 75-80. Buddy has the same truck (2011) in a srw, also tuned and deleted, and pulls around 18 at the same speed. Any ideas on what could be causing this? No check engine codes.

 

some ideas in this thread.....

https://www.ford-trucks.com/forums/1...n-mileage.html

 

__________________
Previous owner could have done some modifications (injectors, etc) in an effort to generate more horsepower... Was the PO towing ? Did it come with a gooseneck hitch setup in the bed? You may have a truck that get's 11-12.5 mpg regardless of being empty or pulling a heavy load....

Hobo

 

When you bought the truck, did it come with the tuner? If not, do you know if the previous owner still has the tuner? The installed tune might not be ideal for fuel mileage. Without the tuner, you might SOL on doing much about the mileage.

Also, lift up on the right foot some. Your best mph whether deleted or stock is around 65 mph.

 

Your comparing a dually to a SRW. Could be a difference in gear ratios, could be different tunes. There is extra rolling resistance of 6 tires on the ground vs 4 not to mention wind resistance of the dually fenders. I would imagine the dually weighs more as well. To many apples to oranges for a proper comparison in fuel mileage.

I get roughly 2 mpg less than other users here with the same truck, only difference is I have Toyo AT tires and they are running stock Michelins.

 

When I had my stock 6.7 2015 DRW, I could get approx 18 on highway with one regen, 15-16 around town with one regen and 10-11 on the road pulling my 35' 5th wheel.

 

What is your engine rpms running at 70mpr
and what is your buddies rpms running at the same speed
l will venture to guess yours will be quite a bit higher due to gear ratios

 

Like most have said, gear ratio most likely and rolling resistance / weight. Wouldn't buy a dually if I were concerned with fuel mileage. 75-80 is not a good mph to achieve good mpg. keep it around 70 and you may do better

 

My '17 F350 DRW gets 15 to 16 mpg in town but only 16 to 17 hwy depending on speed. I've got the 4.10's so I try to limit my rpm's to 2K which is 67 mph and a good cruising speed. Anything over 70 mph it start's drinking heavily!!

 

I'm sure the skinny pedal has something to do with it for sure.

Plus gearing, landscape and headwinds.