lookin forward to the arrival of my 6.7.... plan to do a very specific break in for optimized mpg and power...

 

We drove an hour and a half down into Ky. yesterday to meet up with my UAW brothers and sisters to help clear tornado damage. I was holding her to the speed limit, it felt like we were crawling, and I was getting 21.8 mpg. Then it went into an exhaust cleaning and that was the end of that! Got home with an average of 18.2, mostly highway. I didn't do as well on the way home keeping it at the speed limit. It's great a truck this big can get this kind of mileage, but I really don't care about that too much. Give me the power!

 

You're correct, if you keep it around 55 this 6.7L gets phenomenal fuel economy.

My record is 23.4 MPG on the Natchez Trace one Sunday afternoon when my truck was new over 104 miles I think it was.
It wasn’t busy so I could feather the throttle carefully and never exceeded 55 MPH on the speedometer.

However, I like my 400 horses to gallop so I’ve never seen those numbers since!

 

Just drove from Richmond to Frisco, NC on the Outer Banks ....mostly flat highway and ended up with an average of 18.5 miles. The bet part was before I started out the estimate mileage to empty was 320..... After about 40 miles on the road I had 351 miles to empty. I then filled up before we went over the bridge ....I had 3/4 of a tank and after filling it back up it now showed 444 miles to empty!