Duramax Mileage - Montana Owners Club

jimr · 03-22-2009, 04:06 PM

I just took my first trip pulling the Montana with our 2007 2500 HD crew cab Chevy with the Duramax. Got 9 MPG for the 150 mile trip. Not happy given truck only has a 26 gallon tank. Is this what others with the Duramax are getting. My previous truck, 2000 dodge 2500 with Cummins and 5 speed would get 12 to 13 MPG on same trip. I kept speed at 65 or below. Thanks for any input.

garyka · 03-22-2009, 04:34 PM

My duramax took about 50,000 miles to loosen up.I have 65,000 miles on it and I get a little over 11 miles towing and 18 to 20 on a open road not towing.I forgot to mention I had the Transflow installed.

jimr · 03-22-2009, 05:02 PM

The truck has 54,000 miles on it. The best milage I have gotten around town not towing is 13.

DnDatGrdJct · 03-22-2009, 05:06 PM

We appear to have about the same truck you have. But only about 10K miles on the 2007. When we tow our mileage is about 10-11 driving at 55 mph. When we are not towing we average 18-19. Do agree with you the fuel tank size is not good if you do a lot of towing, especially if you travel, like we do, in areas that have fuel stations a distance apart. We bought two 5 gallon containers we keep in the back just in case.

I think that we are doing about what others experience.

Dean Nelson

Montana Sky · 03-22-2009, 05:17 PM

There are too many variables with only towing 150 miles to make a judgement. winds, winter blended fuel?, terrain, exterior temps, etc... My LB7 Duramax with 125,000+ miles on it averages 12-13 towing my loaded 3400RL and 21-22 mpg empty on the highway. Do you have the LBZ or LMM?

RKassl · 03-22-2009, 11:54 PM

Best mileage is obtained at 59-60 mph, I can hit 12 to 13 mpg.

lawrenceb42106 · 03-23-2009, 12:25 AM

We get 10-12 mpg towing and empty we get 15-17. We have 160,000 miles on the truck. Like others have said 60-65 mph seems best for mileage.

corncob · 03-23-2009, 01:51 AM

My 2006 averages at least 12.5 mpg when I keep it between 59 and 62 mph by gps towing the 2008 3465SA Monty loaded. Best I ever got on an 1800 mile was 20.5 mpg not towing but loaded with 4 adults and their fishing gear, etc. We ran the truck at 75 mph ave. on the interstate.
Around town 17.5 + or -.

Regards

exav8tr · 03-23-2009, 02:04 AM

JimR, You might want to look at www.Transferflow.com. I replaced my 26 gal OEM tank with a 45 Gal tank, of course, there's the extra weight thing and the added cost, BUT, if you do a lot of travelling the added gals made it worth it for me. That's when we had the 2500 Chevy, have since upgraded...

indy roadrunner · 03-23-2009, 02:34 AM

I have the 06 2500HD extended cab long bed 4 x 4 with tow package. I'm getting 11 to 12 depending on how much over 63 mph I run. Not towing mostly interstate travel to work I'm getting 18 average. I have found that when towing over 65 mph that thing starts guzzling the fuel. 60 to 63 seems to be the sweet spot.

mail2us · 03-23-2009, 04:30 AM

Jim, we tow a 2008 3400 with a 2007.5 Duramax 2500HD CC, 4x4 Z71. It is the LMM diesel as it is the new body style changeover from the Classic model. We do not travel heavily loaded and travel at moderate speeds, never at 65 or higher. Our mpg depending on road conditions, etc averages about 11.5 to 12.5 when towing. I do use the Tow/Haul mode and that could affect efficient MPG, so I'm told. Without load or not towing we get 17-18 mpg. I have a shortbed and a small gas tank @ 26 gals. Dennis

HughM · 03-23-2009, 04:43 AM

We have 17,000 miles on the Duramax and at 60-62 mph we get 11-12 mpg depending on the wind. I use Tow Haul until 45-50 mph and turn it off.
Not towing I'm getting 18 mpg city and highway and 20 mpg at 60 mph,

TLightning · 03-23-2009, 09:39 AM

I cruise at 62/63...that keeps the tires under their speed rating of 65, gets the Allison in 6th gear, and gets better mpg than faster. I average 10 to 11, run with the T/H engaged (that's what it's for)...head winds do the most damage to mpg. For a day's trip, the worst mileage I got was under 9, going into a 35 mph head wind. The best I got was 13.3...with a tailwind.

mcgiver2 · 03-23-2009, 11:37 AM

I haven't checked mileages i just add extra tank and let it roll,,,,,,,but i did travel 1100 miles +/- on 80 gallons

drknapp · 03-23-2009, 12:07 PM

I have a 2007.5 2500HD 4x4 SB. I average around 12 towing my 27' SOB.

TAKPAK · 03-23-2009, 12:53 PM

With our 2008 Duramax and 14,000 miles on it, I am getting 11 to 12 MPG towing the 3400. I set the MPH based on the engine RPM's. The maximum torque is reached at 1600 RPM's, which is around 58 to 59 MPH. If on "flat" ground, I take it out of T/H mode so it'll go to 6th gear. If on a hill, going up or down, it goes back into T/H mode. Empty, city driving is running around 16 to 18, empty highway is running 20 to 22 MPG. We have the extended cab, which must make a difference in the fuel tank size as our tank holds 36 gallons.

lfw · 03-23-2009, 01:45 PM

We have a 2004 Duramax with 83,000 miles on it.. Gets about 22 on the road, on nice flat ground in Ohio.. About 17 around town.. The best we have seen is 15 pulling the 2008 3000RK around Atlanta..Weight it today with the truck.. 17,900...A lot of weight for the old Duramax for sure.. Usually it runs about 14 mpg.. Only use T/M when it town or going down steep grades.. We did install a Super Chip a couple of years ago..
lfw

billhoover · 03-23-2009, 02:05 PM

I get around 10 +/- when towing and 18/19 when not towing. Just my 2 cents, but I would not recommend anybody with a 3/4 ton getting an extra fuel tank. The last thing they need is more weight.

jimr · 03-23-2009, 03:27 PM

Thanks for the feedback. Took it to the dealer today to have it checked out. Replaced the air cleaner and they found a leak in a power stearing line and trans cooler line. Since I bought the truck used I had them replace the fuel filter and external trans filter since I din't know what their service interval had been. I am now $735 poorer. I am going to haul the Montana from Boise to Moses Lake WA next weekend so that will be a real test. I will keep it between 60 and 65 and hope for the best.

goin2themountains · 03-24-2009, 08:37 AM

One more for around 10 towing, and 18-19 empty. I have considered a transfer tank, but yeah, can't get past the weight issue. Oh well, fueling every couple of hundred miles gives me a chance to get out and stretch anyway. Enjoy your trip.

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