I've already posted this a couple of times, but here it is; the best fuel economy I've ever seen in a diesel pickup. A couple of months ago I got MPG crazy and came across these articles in my research.

1997 Dodge Ram 3500 Dualie Cummins - Diesel Power Magazine

That's a 12V Cummins dually that gets 30mpg.

And this:

2000 Ford F350 Power Stroke Diesel Truck Mileage - Diesel Power Magazine

That's a Powerstroke 7.3L F350 2WD that gets 26mpg.

I've not seen a test conducted on a Duramax, but seeing as how my '03 can get 23mpg if I drive easy in warm weather, I have no reason to believe that a duramax couldn't surpass 26mpg with similar modifications. If I had a 2wd regular cab to use as a test mule, I'd try it out. Also with EFI live, I bet you could make a fancy tune to sip fuel below 2000rpm right at 60mph

 

Its not hard with my LBZ to obtain 24+ mpg hand calculated.. at 55-60 mph on the highway. I think anything over 15 mpg is a great number, considering what our trucks weigh. With the proper setups, I see no reason that any 5+ liter turbo diesel couldn't achieve 25+ mpg on the highway.

 

Any number over 15 certainly is good, especially with the way I drive in the city

 

i run at 17 or so, about stock. 07 chevy 2500 gasser, well about 9 with just my tools 6-7 fully loaded with a trailer, and thats bone stock, well power wise.

 

mine gets bout 18 city, 22+ highway
04.5 cummins, muffler delete, 48re

it beats most midsize suvs though!

 

14

 

I get around 18.5 in town and 22ish highway. i bet a bed cover and more air in the tires would inflate that number a bit.

 

hey mythbusters say that a bed cover doesn't make a difference

 

crabelle gets 33mpg with his 12v

i get 17-18 with my 04.5

 

you guys get good mileage i get 18 on the highway 13 in town. 1998.5 24 valve