My 2016 F250 4x4 with 6.2L and 3.73 gears makes 6.0 mpg towing a 6 x 15' aluminum toy hauler at 70 mph. Toy hauler is 10' high, has tandem axles, and only weighs 3500 lb. All tires are properly inflated, no brake drag, no uneven tire wear. This is in flat country (North Dakota).

Truck has 8500 miles. Empty on highway I get 11.5 mpg with winter gas and 12.5 mpg with summer gas. All numbers are calculated by hand.

I contacted my dealer. His response was since there are no service bulletins on it, there is nothing he can do. Anyone have any suggestions?

 

Is that right 10' high? If so you are probably getting a lot of drag from the air going over the truck.

 

3.73's and towing are not a great combo. What tires you running?

 

9' is a more accurate height to the roof line. It measures 9'9" to the top of the air conditioner.

 

Tires are 275/65R20 (standard tires with Platinum package)

 

With my 3.73's i get 8 with my rather light 21' toy hauler in the non flat terrain of the PNW.

 

Oh yep you need 4.30 gears. I just ordered my new truck with them.

 

80% of my driving is non-towing. I was sure hoping for better mileage when towing such a light load. I have never seen anyone else post such low numbers even with much heavier towing loads.

 

You have 34.2" tires. Stock is 31.5". If you had 4.30 you would be turning 100 more rpm at 60 mph vs stock 3.73. Many mpg reports you see are not with 34.2" tires. I'm not a fan of my 3.73's. My good friend up north has your exact complaints with his 2015 3.73 and 33" tires.

 

I have 34" tires and I get 12mpg unloaded on average.

I get about 8mpg or so towing my 7000# camper going 70mph. I'd definitely go 4.30 next time around. But I'm going diesel on my next truck! I hate having to share gas pumps with the cars when towing.

 

Slow it down for better economy, also the wind can play havoc with mileage

 

This^^

It's not the weight that's getting you, it's the wind. I'm towing just over 12K with a 5'er that reaches 13', and I'm getting 7-7.5 mpg at 60 mph in moderate winds and rolling hills. Even rolling solo, you will see a big difference in mpg driving at 60 vs 70, especially in a gas truck. These trucks are as aerodynamic as a barn turned sideways. Adding a box trailer to the back end only compounds the problem. When I had my 24' enclosed trailer, I NEVER towed it at 70, even empty.

Being in ND myself, some folks reading this may not understand that we call a 30 mph wind up here a gentle breeze. And we don't call it "windy" until it goes above 50 mph winds. It's almost never not "breezy" here. I feel a big hit in my gas tank when that "breeze" turns into a headwind.

Also check your tires. If you're running ST "china bomb" tires (like most trailers), they are likely only rated for 65 mph. Just something to think about as well.

 

I usually do 7-8 pulling an 8klb travel trailer, although I'm only doing about 65

 

I am getting 7-8 mpg when pulling 14k on a gooseneck trailer but I only hit 60 mph on most trips. I an averaging around 13 mpg unloaded. I was around 11-12 unloaded mpg until I hit 4K on miles, seems to be getting better mileage now.

 

of those air deflector wings on the cab may help to increase mpg. They direct the air up and over the trailer instead of hitting the trailer head on.

I have a 16' boat I pull with my truck that is less than 1000lbs including trailer. Basically no weight but I can tell it is back there on the highway as mpg is reduced. The boat catches tons of air and causes drag. I'd probably pick up at least 1mpg if I put a travel cover on it.