have had my third Duramax and this one has terrible fuel mileage compared to the first two... the newest one is a 2007 and has the diesel particulant burner, not sure if this is part of my problem as I've heard of others in the same situation... have put a Airraid filter on it, plus using a Hypertech programmer, and no difference so far in fuel mileage... I'm currently getting 17 to 18 mpg on the highway, my last one with the same equipment on it (minus the DPB) got approx. 25 mpg... anyone else having the same problem and does anyone have a solution? any help would be greatly appreciated.

just did a three hundred mile trip and avg 18.4mpg running ppe on 220hp tune and cruise control on 65-70 mostly. just changed fuel filter too. What mileage did you get before hypertech? bigger tires?

17-18 this time of year probably is not that bad, I can get 21-22mpg in the summer highway if I'm easy on the pedal. I don't think you're gonna find many people that can honestly say they can get 25mpg.

no way your gettin 25mpg especially in the winter, with winter blend fuel

Funny coincidence my DIC shows I used 4000gals when i pulled in driveway so:

63,240 mi. divided by 4,000 = 15.8 mi per gal
63,240 mi divided by 1,570 hrs = 40.2 mi per hr
40.2 mi divided by 15.8 = 2.5 gal per hr

This is from probably 70% high speed highway driving (meaning 75mph +)

Running stock sized tires... and no change with the hypertech... my last truck was honestly getting 25 mpg. Is this having to do with the diesel particulant burner possibly? Ive heard other complaints as well since GM added this burner...

Also - a few friends with 2006 trucks - with same equipment as mine are averaging on the hiway about 26-27 mpg (canadian gallons!). Why does my '07 get such crappy mileage compared? Whats changed?? (other then the added diesel particulant burner).

I get 25 mpg in the summer Imperial Gallons but in the winter that drops down to 18 - 20 due to winter fuel...

If I load up on additives and sunoco gold fuel I can get better in the winter at around 22 mpg but not much more...

sounds like your average...

Probably a better question to ask on the 4th generation section. In general the DPF will cause increased usage. Much debate on how much though. Secondly and most importantly winter fuel is horrible and in particular I think mine is down far lower this year then most. It is colder so do they mix the fuel differently or is just from the cold? How old is the truck? Mine took 17K or better miles to loosen up and probably 4K of those miles were towing my 5th wheel. Don't have a heavy foot, use the winter and sweat it out to the better fuel in the spring and until your truck has some miles on it. The filter as you have noted isn't doing anything and that includes filtering as good as the stock one so pitch it.

The best I have seen on mine is 21.7 us gals. all highway @ 70 mph most of the time 18-19 is normal. 90% of the time mine gets anywhere from 13 mpg to 17mpg combined. The 13 mpg came last week when it was 8-15 degrees F at night and 28-35 degrees F for high temps, all city driving though. Since it has warmed up this week my truck is back to 15 mpg city right now. However mine usually gets 15-17 all the time depending on my right foot. I have been pleased with mine but this is my first diesel and I have nothing to compare it to. The mileage I stated for my truck is for the last 2 years of owning it.

My mileage is similar to TDMAx07's, filled up yesterday and recorded 18.2 mpg (US) I'm happy with the mileage I'm getting since this is my first diesel. In the summer I should see a slight increase. My truck is an 07 Classic 4x4 D/A combo cc

SP

I just calculated mine.... 14.7 avg since last fillup in the 07 reg cab LBZ. Mixed highway/city and a little heavy footing it since the PPE... I just filled up last night and am going to take this tank easy.... Lets see how it does then.

Are Canadian miles per gallon different than US mpg?

You all need to figure out how to hand calulate mileage. I don't care if you are running water injection and propane, you just aren't going to see 25mpg with a 7,000+ pound truck. Period.

You all need to figure out how to hand calulate mileage. I don't care if you are running water injection and propane, you just aren't going to see 25mpg with a 7,000+ pound truck. Period.


X2

first off Canadian gallons are imperial which are 4.54 Liters and a US gallon is 3.785 Liters... I do hand calculate and my '03 did get 25 mpg highway... already took the filter system off my truck. running the Hypertech on level 2 - and still getting 14-15 mpg on the highway... I realize that Winter diesel isn't the best to use for maximum fuel mileage, but am also running a cetane booster as well... I'm also gonna go post this on the 4th gen site as well. thanks for the input guys.

so unless my high school algebra is off and thats not out of the question either,using the numbers you supplied
4.54.....3.785
---- = ----
25.........X

94.62
------
4.54(X)


X=20.84



so your 25 mpg using imperial gallons is equal to 20.84 mpg for those of us using US gallons to calculate mileage,thats a lot more believable. You need to compare apples to apples.

IMHO 17-19 highway is very good for our trucks anything over 19 is a great but rare. There are so many varibles that effect mileage so it's hard to say what is causing poor mileage. I think in most cases the driver is the problem.

but that's getting off topic... that was the '03, right now i'm trying to figure out how to get more out of the '07.5... thanks for the input...

I would say get rid of the dpf and use efilive to turn off the whole dpf system and straight pipe it.

but that's getting off topic... that was the '03, right now i'm trying to figure out how to get more out of the '07.5... thanks for the input...

his sig say's it's an 07 not an 03.Or did you mean your other one was an 03.