Took my first trip this weekend to Montana.....about 1200 miles total......now have 1720 Miles on the truck.

Fuel Mileage was extremely speed dependant:
65 MPH - 16.7
70 MPH - 14.4
75 MPH - 13.2
80 MPH - 12

This was all shown on the overhead computer.

The 70 MPH vibration can be explained as a Harmonic vibration through the steering wheel, pedals, seat, and everything else! It is horrible. I found myself driving at 69 MPH where the truck is super smooth.

Otherwise, everything else on the truck was awesome. They have gotta fix that, and fast.

Does anybody think this could be one of the reasons that the mileage suffers so much above 69 MPH? Or is it just the power required to push a brick through the air.

 

I have driven mine at all speeds (up to 90MPH) and never noticed any vibration.
Maybe I'm just one of the lucky ones.
You are right on about the milage being speed dependent.
If I were not always in such a hurry, I would get GREAT milage.
If fuel prices keep going up, that may tend to slow me down a bit.

 

I guess I got lucky also. No vibration. I notice the speed dependent mileage, but have to add that it was the same on my 01. I just made a 2000 mi. round trip. All interstate. Used cruise most of the way and kept it set at 80-82. Avged. 15. I'm not complaining since it weighs almost 8000 lbs. and on the return I was bucking a 20-25 mph. headwind.