Have a friend that bought an '08 4x4 (SC/LB) with the 3.55 axles. Not getting much chance to drive it, so I offered to do the "ring break-in" for them. I took the truck for a nice drive and saw the fuel computer was at 14.5 mpg. They have never reset it since purchased and it has only 900 miles on the truck. I know that the meter is not always that accurate, but I was impressed, since it's about a mile per gallon (or more) better than my 6.0 gets in the same driving (lots of hills and twisties which aren't keen for MPGs).

I'm betting that an all fwy trip will see it in the 20 range w/o much problem. I was wondering if others with 3.55 4x4s have checked mileage and what they're getting?

Oh, and the '08 is quite a nice upgrade compared to my '07 -- really like all that they did with the new truck. Alas, my '07 goes to the grave with me, or so my wife says (I'd better not let her drive an '08 or that may be sooner than I think!)

 

On the highyway 16's with a 2.5 leveling kit and 35 tires. In town 12's, now the sad part. On a trip pulling my 14k 5th wheel in the 6's while my friend with his 08 Cummings motor home gets in the 12's. Sad but true.

 

Wow, that is sad. I run close to 22K Gross weight, fully loaded with camper, horses and gear. Worst I've done is mid 9s and that was in very hilly country. But I push well into the 12s on a milder trip. Maybe you should've bought a cummins like your friend? (no g by the way)

I have yet to even hear the overly optimistic RV salesmen to quote a number like that on a motorhome with a 6.7. They'd love to get their hands on your friend's rig...

 

Any 2008 with 20" rubber has the same gearing as the 3:55 ratio trucks.

 

Before I bought a diesel most people, with Fords, Cheys and Dodges towing said 18 mty and 12 towing. Talk can be exagerated. On short runs some people can can those milages but not over a longer period of time. Towing our close to 17k 5ver averaged 8.76 for 2,000 miles and 13.46 for 4 tanks after towing last fall. My last tank has only been about 10.5 on the computer short runs, regens, towing camper around yard and short trip. So we are anxious to find out how the new 3.55s are going to work out on a longer average. Hoping to hear that magic 18mpg number