Duramax Mileage - 22 MPG? - Page 2 - Diesel Forum

Dave Whitmer · 08-21-2008, 09:19 PM

I don’t believe it. Not with a high-revving engine and a loose torque converter and a 4x4.

On several occasions I have challenged blow-hard champions of both Duramax and Cummins engines to a witnessed road trip to measure actual real world fuel economy. Always the blow-hards find some reason to beg off.

I routinely get 24 MPG in the worst of conditions (winter) and am pushing the mid-27s in summer driving. I drive the posted limit on Interstate and rural roads and run with the traffic in town. Obviously that is empty.

Anybody want to call BS on me, my response is always the same :ROAD TRIP. Put up or shut up. Better yet, I’d like to get some of these guys with their BS claims about Duramaxes or Cummins in a fuel economy test. Loaded or unloaded, slow or fast. I’ll whip their socks off.

BTW, my truck with its 3.08 gears can tow anything that will attach to the factory hitch. In fact, it will tow a good deal more than it can stop.

scrmn6guns · 08-21-2008, 10:29 PM

Well here is what I know... a good friend of mine has an 03 durmax, 3/4 ton, 4X4, crew cab. He has 285's on it with a superchips programer (unk which one). we have taken it on several hunts across country and the best we have gotten is high 17's. This was with a lite load (not towing). We tried several different speeds and the BEST we got was high 17's. So I thinlk if the guy is stating 22 mpg he is trying to sell the truck with infalted claims on the MPG......

Kaliburz · 08-22-2008, 12:25 AM

Quote:

Originally Posted by Dave Whitmer

I don’t believe it. Not with a high-revving engine and a loose torque converter and a 4x4.

On several occasions I have challenged blow-hard champions of both Duramax and Cummins engines to a witnessed road trip to measure actual real world fuel economy. Always the blow-hards find some reason to beg off.

I routinely get 24 MPG in the worst of conditions (winter) and am pushing the mid-27s in summer driving. I drive the posted limit on Interstate and rural roads and run with the traffic in town. Obviously that is empty.

Anybody want to call BS on me, my response is always the same :ROAD TRIP. Put up or shut up. Better yet, I’d like to get some of these guys with their BS claims about Duramaxes or Cummins in a fuel economy test. Loaded or unloaded, slow or fast. I’ll whip their socks off.

BTW, my truck with its 3.08 gears can tow anything that will attach to the factory hitch. In fact, it will tow a good deal more than it can stop.

I'm sure truck did not come w/ 3.08 ratio, right? What made you swap the new ratio in?

Well, if you're getting high 20's, then that guy w/ a Dodge w/ a 3.04 ratio and OD manual tranny must be getting similar (at least he claimed that).

Dave Whitmer · 08-22-2008, 06:57 PM

Til some decent testing is done its all just a CLAIM.

Kaliburz · 08-23-2008, 01:52 AM

Dave, how did you decide to put a 3.08 ratio in?

chris u · 08-23-2008, 03:06 AM

I have a 97 f250 stock I got 17 mpg. and now with the upgrades I only get 15mpg. see upgrades bellow all this is not towing and granted it sounds better now may give it a little more throttle just to see the smoke roll out lol.

Quicksilver Ram · 08-24-2008, 04:47 PM

I drove over 800 miles yesterday in my Cummins. Most of it was mountainous highway running 75-80 and about three hours of stop and go in Riverside and San Diego. My overhead readout says 21.3 and mileage hand calculated was 18.9. Heading back to Vegas I didn't spare the ponies so I know I could have gotten better. I would say 22 mpg is attainable if the speeds are kept down and the drive is all highway. Of course, a lot of it is the driver. I'm a truck driver and know how to get the most mileage out of a vehicle: coasting whenever possible, maintaining a constant speed, no fast acceleration, no excessive speed, etc.

Dave Whitmer · 08-24-2008, 05:46 PM

How did I decide to put in a 3.08? I couldn't find a 2.73 to fit a 10.25" Sterling Axle.

By slowing down the engine at a given road speed, you reduce the engine frictional HP. Less engine losses equals less fuel burn at a given road load.

I am heartbroken that an overdrive costs so much for a 4x2.

Re: Post #21
I'm not surprised. The big tires and lift robbed your MPG.

Kaliburz · 08-28-2008, 03:28 AM

Ah. I see.

Yup, you are right, OD's do cost a lot. If your manual tranny is a ZF, yup, man, GV really wants a kings ransom...

navistar45 · 08-29-2008, 09:33 PM

last time i figured mileage on the 82 gmc in my sig was about 6 years ago. 4spd tranny,3.73 gears and 60mph, i could average 21mpg. the 82 chevy 4x4 is exactly the same, but has 4.10 gears. 17 is the best it will manage, at 60mph. a 90 model dodge i had with 3.07 gears and a 3spd auto, 22mpg at 60mph was possible with it. the 91 dodge i have is 4x4 4.10 gear equipped, and has a 5spd manual. 18 was the best i could get at 60mph. my 05 dodge has 3.73 gears and a nv5600 6spd, 19 was the best it would fetch at 70mph on older style fuel two years ago. my 02 ford has a 6spd and 4.10 gears, same conditions, it would match the dodge. my old man onece had a 1/2 ton 6.2 chevy with 3.07 rear, and a 3spd auto. 25mpg at 70 was easy to net. i have found over the years , all trucks when driven and equipped the same , will just about match one another on mileage . latter dodge auto's[04/05 model] seemed to do a bit better then the ford or gm's, i suspect due to the higher ratio od.