My dad is one of the most conservitive drivers I know and his 08 Mega Cab 2500 Mega Cab 6.7 Auto averages 17.5-18. Thats 75-80% Highway. He drives from Southeast Kansas to Altus Oklahoma where hes a senior engineer for a aircraft company and thats about 6 hours. He accelerates easy like someone should not like me at all and thats the best he will get. Thats also running 70mph. He just rolled over 15000 this month. I cant wait to get a 6.7 with the 6speed and 3:42's.

 

how are you calculating the milage? you can't go off the speedo with 35 and 37" tires, so how are you getting accurate distance readings, is you truck chipped and the chip recals your speedo? Because the largest tire size the dealer can input into the computer on a 6.7 is a 285, I don't know what gears you got, but I have with 3.73 gears and stock tires i'm turning 1700 at approx 65mph,and get a hand calculated 22mpg on the highway

Does the 2wd truck come with 3.42? i thought the 3.73 and 4.10 was only avaliable

 

With 16k miles on the truck I'm still only getting 9mph towing the 5er and quads (14-15k lbs.) I just returned with a horse trailer and pickup bed full of hay (8-9k lbs) and averaged 11-12 mph over 500 miles. I remind myself that I am towing more weight and maintaining better speeds (70mph) with this new truck and that costs... I don't drive the truck empty very often but have seen 17mph on the highway. I haven't driven in city traffic enough to know what the mileage would be. I also blame the emissions control devices on these 6.7's.

 

With 4000 miles on my 08, as stated in another post the best I was getting was in the nines towing, 12's city and 14's highway. I also put an mp8 on the truck thinking I would pick up at least 1-2 per gallon. The mp8 did nothing for mileage, at least in city/highway driving, so in 3 weeks I will be headed hunting/ filming expedition on a 1500 mile trip one way so I will see if I get anything better out of the mp8.

flgc

 

As an added note, my 2008 has the 68RFE trans with 3.73 rear end; SRW, and tachs 1750 rpm at 70 MPH. This is exactly 300 rpm lower than the
"Powerjoke 6.0" that I had previously and I'm sure it's due to the final
overdrive ratio of the 6th gear.

 

I now have 27k on this truck and if I am careful I get 14 maybe. With the Attitude kit I get to watch the egt's and runs super high on flat ground and no load, easily 12-1300 degrees. When "REGEN" come on which is quite often will easily run to 14-1450 instantly. I need a way to bypass this crap! Changed tire size and doesnt seem to make much if any difference

 

I now have 27k on this truck and if I am careful I get 14 maybe. With the Attitude kit I get to watch the egt's and runs super high on flat ground and no load, easily 12-1300 degrees. When "REGEN" come on which is quite often will easily run to 14-1450 instantly. I need a way to bypass this crap! Changed tire size and doesnt seem to make much if any difference

 

Less than 1,000 miles here on a brand new engine, but 350 mile 65-70 mpg highway trip through the rolling hills of western PA/WV gave me 16.8 mpg (and climbing) on the overhead. Around town (lots of hills), 13.8. I'd say you need to get that RRT ECM flash for the soot problem.

 

I just put 2700 miles driving from Idaho to Alaska last week after picking up my new Megacab....13 MPG with 35's was the best I saw on the overhead.