"Real World" diesel fuel mileage on Duramax

[jcmseven]

My experience has been that diesels in general and the Duramax specifically, vary much less than gas powered vehicles due to speed. Trucks are aerodynamic bricks, and even diesel trucks' most challenging issue when it comes to fuel economy is overcoming air resistance, especially at speed. That said, just yesterday I was at my parents' place and met my wife for an appointment at our kids' school before heading back home. I was late and drove really "too" fast to make it on time. On the highway, doing 80+ (I won't say how much more) much of the drive my mileage on fill up was 16.8; not as good as usual but not the precipitous drop one would see with a gasoline vehicle changing gears constantly to maintain speed.

John M

 

[Superduper]

Well finally got a chance to take a break and enjoy my new truck. Wheel size should not make a difference -- these are not aftermarket, they are factory forged optional rims. Speedometer seems right. Tire profile might be lower than the 17 or 18 inchers. Anyhow, so far, steady 18mpg.

 

[Bob77064]

Good looking truck.

 

[Dmace]

Very nice!

 

[WilliamBos]

Nice truck!!

At $6+ per gallon for gas, I am thinking real hard about a DMAX for my next truck. I am sure it will get the same or better mileage than my 5.3L does now.

Would you occasionally update us on the mileage please?

 

[Reg]

I have an '03 one ton chassis cab with Hillsboro aluminum flat bed.
It has the two sets of trip odometers, gallons, MPG, avg speed, etc.
I use one for towing and that is currently at 14.6, the other for when I have no trailer on, that set is currently at 18.7.

The trailer is usually a 38 something foot head to head horse trailer, occasionally a 10K equipment trailer.

A couple of notes;
Because I am hauling horses I may be driving a bit softer than I would with something else of same/similar weight back there, so my 14.6 may be a bit higher than most folk would get.
The 18.7 without trailer mileage is just about no highway, i.e. very short local runs for things like inspection sticker, dump, lumber yard, relative's couch move, i.e. all short and cold.
I could do better than that (-:

These are both corrected for ACTUAL distance and ACTUAL gallons, not just what the meters say.

As I tell everyone, fuel (dis)economy is much more about HOW you drive than WHAT you drive - add WHERE you drive to that.

This may be interesting to some, not to others.
I have figured back that my gallons per hour is pretty much the same whether I have the trailer on or not. i.e. a load just slows me down.
Maybe not surprising, my foot has the same "weight" on the pedal, my other senses tell me to keep the load/strain about the same.

YMMV - and most probably does.

 

[Reg]

OK, now that I have read some of the other replies;
Mine is a DRW.
Long/short bed is irrelevant, since it had no bed.
Axle to cab is 60 inches, which is the relevant measurement, about 2 inches more than the "long bed".
Regular cab.

Don't get too carried away with what the DIC says.
From time to time I have zeroed mine out on a cold and frosty morning while waiting for the glow light to go out.
HORRIBLE fuel usage to the end of the street (1/4 mile) gradually improving over the next 3 miles to the first stop.
Turning around at the barn WOW, that alone just drank my lunch money.
It takes a long time to smooth out to a valid representative average.

If nothing else the "inst econ" display just might get you out of contesting lane drop/merge situations (-:
With horses I don't contest those anyway.
Passing slow pokes is EXPEN$IVE, so I rarely do that.

 

[jeffster]

2012 GMC Sierra CCSB SLT. Have about 1200 miles on it and most of it is hilly country driving and getting around 17mpg mixed. That is with the 265/70/18 Michelin LTXs that came with it. My previous truck was also a Dmax, 2006 CCSB with 255/85/16s Toyo M55s and was getting around 14mpg mixed. Previous tires were 265/75/16 Goodyear Duratracs and mileage was around 14.5mpg mixed. So, overall I am fairly happy. Going to need a more aggressive tire here though soon, so hopefully it won't take down the mileage too much. Will also maybe go up a size or two and level it.

 

[WilliamBos]

2012 GMC Sierra CCSB SLT. Have about 1200 miles on it and most of it is hilly country driving and getting around 17mpg mixed. That is with the 265/70/18 Michelin LTXs that came with it. My previous truck was also a Dmax, 2006 CCSB with 255/85/16s Toyo M55s and was getting around 14mpg mixed. Previous tires were 265/75/16 Goodyear Duratracs and mileage was around 14.5mpg mixed. So, overall I am fairly happy. Going to need a more aggressive tire here though soon, so hopefully it won't take down the mileage too much. Will also maybe go up a size or two and level it.

What is the ratio of DEF to Diesel?

 

[jcmseven]

Superduper, I do not know if you live in a region that get much bad weather or if you drive on graveled roads much, but I have a set of the GMC molded splash guards on my truck. I have never been much on the look of those type guards, but the GM ones are not so long and are not too noticeable but they make a tremendous difference in the protection of your side steps and rear kick panels. The way those are shaped on the GM trucks they serve as a target for every rock and bit of road debris you go across. I have been most pleased with how much the guards have helped keep crap off the sides of my truck. Especially handy for black or darker colors as those little chips can be seen. This is not a fuel-related response but one based on the pix of your nice, new truck. It's a beauty.

John M