[theTwinsDuramax]

We just got back from a long weekend out to Phoenix and back a little under 1000 miles. I love driving my truck is all I can say, and I know it will only get better with mods. I ran about 65-70 out and got 11.3 calculated (11.5 dic), and returned at 75-80 and 9.8 calculated (10.2 dic). I was tired and in a rush to be home.

 

[youngone]

I just got home from camp and got 20.75 calculated. This was for 520 miles at 65 mph.
I am happy with that.

 

[theTwinsDuramax]

What are you doing to get 20mpgs stock? And what were you pulling; how heavy?
I was pulling my fifth wheel, it is just short of 10k.

 

[diesail]

I'm stock and just did a 1200 mile tow each way. Pretty much the same numbers as you, can see the 11's if I keep it under 70. Seems 1800-1900 RPM is the zone. Can't believe how sharp it drops off after that. As for 20, seen those numbers two under ideal conditions, basicly cruise set 65-68 mph, flat land, no traffic and so on.

 

[theTwinsDuramax]

...best case conditions

I have experienced better on some short trips around NM, around 14 but in best case situations. One while traveling on the down hill side of things for about 75 miles and the other with 30 mph tailwind. Both times I kept it just at 65mph. It does seem as soon as you get past that it has an immediate effect on the mpg's.

Also my DIC seems to stay within 2% of calculated, better and worse.

 

[GMC4Me]

That would be 20.75 liters per kilometer I would wager.

Your mileage sounds really good for a low mileage truck. It should get a bit better with some more mileage. Now that mine is broke in I get about 15mpg light and 8-10MPG bumper pulling around 10K at 60-65mph with the occasional 80mph pass and a grade pull, and that is also with having the 4WD penalty. Having the cruise control keep it in the RPM sweet spot and letting the Allison do its thing is the key to good mileage.

 

[dieseldoc]

We just got back from a long weekend out to Phoenix and back a little under 1000 miles. I love driving my truck is all I can say, and I know it will only get better with mods. I ran about 65-70 out and got 11.3 calculated (11.5 dic), and returned at 75-80 and 9.8 calculated (10.2 dic). I was tired and in a rush to be home.

I towed my old 35 foot 5er (10,000lbs) about 10,000 miles the past 2 years. Found best mileage towing was to keep it in 5th gear and keep speed around 65 - with that can get around 10-11 consistently. Can get higher on short runs but I'm sure its only because the DPF didn't regen during the short trip.

 

[youngone]

Im happy with 20.75 mpg the truck only has 3800 km on it. Thats even with winter fuel so it might get better. I have never towed anything with it yet.

20.75 mpg was on a trip of 520 miles. the dic was saying 13.6 liter per 100 km.

 

[09BLKDUALLY]

For the info of those south of the 49th parallel (Canadian Border) multiply the candian mileage by 3.785/4.54=.83 to correct the Imperial Gallon to the US Gallon 20.75 x .83 =17.3 mpg US equivalent. Still not bad for a new truck with winter fuel.