So went on a longer trip 265 miles and the overhead said 19.5mpg but by hand calc did 20.4mpg. Did the same on the way back 20.5 mpg.. Cruising at 68 mph at 1700 rpm the whole time pretty much some up and down hills on the way from NY to VT. Very impressed so far and just broke the 2000 mile mark on the truck so hopefully it continues to rise...

 

Nice MPGs especially with so few miles. Should just get better from here on out.

Be glad yours says your getting worse then you really are. Mine will get your hopes up and then you hand calc it and get roughly 2 MPG less...

 

yes i was shocked myself, but wanted to double check and with the 6 speed auto seemed the mpg went up going 68mph then cruising at 55-60. What does everyone try to keep their rpm's on the hwy?

 

i try to keep mine around 2000 but with my 4:10 gear that only puts me around 65 MPH and if the speed limits 70 i like to do 5 over. i think on average i run 2400-2500 RPMs while highway driving...

i think i once read that these trucks put out the best milage between 1800 and 2200 rpms while on the highway but thats only what i think i remember[:-]

 

WOW, that is awesome mileage for a 6.7 ctd. Today I had my computer flashed and kind of hoping it will do a bit better mileage wise. I was only getting 13mpg on the highway at 75-80mph at 2500 rpm. Not impressed. I have an 06 six speed manual drw and you would think it would get better than that. In town I get about 14 or so. And all of these numbers are calculated out. I would love to see 16 on the hwy.

 

inferno try slowing down to 68-70. probally see a huge increase in yoru mpg. also i notice my mpg increased when the jake brake was off then was on even though I did not hear it activate..