With our new 6.7 with 1600 miles on it. We decided to go from Michigan to Orlando via I 75. This included flats to 6% grades. Towing a 13K fifth wheel.
I was amazed on how it handled traffic, mountains, etc and most of all got 10.3 mpg..loved the large fuel tank except when had to pay.
Roads on 75 was very bad on some spots. Lots of construction. Instead of a drive time of our usual 20 hrs it was a 25 hr drive. Oh yes several storms to wash the unit.

 

I hear you on being amazed. I am still surprised after three years how well mine does.

 

Great report. I seem to average around that for mpg's as well.

 

Nice ride bigredtruckmi. Just curious as to the axle ratio? 3:73 or other?

 

4.30 it has the max tow pkg.

 

Dave, I averaged 9.9 mpg towing from Orlando to Milton, Ontario. Trailer weighs 17K.

 

The extra 4 K made a difference. Still very good for,what is being towed.

 

I just returned yesterday, my first pull with the new 6.7. Just shy of 200 miles (each way), mostly flat land with very few stop lights. I followed the posted speed limits (up to 65); load was a 10K 5th wheel. 14.44 MPG round trip.

Axle: 3.31

 

That is good mileage towing.

 

About what I get empty.

 

That's about what I got on my recent 1500 mile round trip towing a 14.5k lbs fifth wheel from northwest Houston to the Davis mountains and back. My 06 with the 6.0 got 10.48 mpg. It has the 4.10 rear end and is all stock. Actually would have gotten a little better mileage but I had a turbo hose blow and I wasted a lot of fuel limping along the highway trying to find a parts store. (That tank of fuel got 7 mpg)

 

We blew the same hose last year on our 04. Really loud bang when it went. Then no power and lots of,smoke.

 

I can say that duct tape does not fix everything. 😢

Yes, we had the same bang that sounded like a tire blew out and truck felt like it was in neutral trying to pull our big fifth wheel.

 

I did a 2000 mile round trip with a 10k load on the trailer with my 7.3 IDI. I got over 14 mpg while loaded. After dropping the load i went back up to 20 mpg.

 

I'm a little over 1600 mi into our trip and I thing the running avg will be around 9.0 after all said and done.