Chevy / Duramax MPG?

[RACE427]

"Smoking"

I believe the guys who are reporting these outrageously high MPGs must be smoking some good stuff as they drive their rigs down that long lonesome highway. Either that or they are sucking on diesel tailpipes!! :-laf

 

[steved]

But then you get a smart arse like me... this happened last night, but has happened before...



I was fueling last night... first I had been in the truck since driving it home last Friday night (drove from Fayetteville, NC to Reading, PA without a fuel stop). I was pulled between a new Duramax owner on one side and a PowerStroke (older non-Superduty) on the other. I believe they were friends, as they were talking about other stuff.



They started talking fuel mileage... to which I said I had driven in from Fayetteville on this tank (keep in mind I do have an auxiliary, which I was filling at the time). I told them I expected at least 20mpg, to which they both laughed.



I then said, since YOU'RE standing here, here's the calculator and here's my fuel log (which has every fuel stop since it had 140 miles on the clock)... I said, I'll fill the main tank into the filler so you know its full and fill the auxiliary and YOU can figure the mileage.



I filled up as indicated, and they figured it out... 22. 5mpg. I then told them if they didn't believe that, calculate the last five tanks... they declined. I then said, "yep, that kinda mileage with 4. 10 rears... "!! They both walked away... :-laf



They never did really say what they were getting for mileages... :-laf

 

[fox]

A D-max guy came up to me and said he was getting 23 highway and towing was 16-17. I said Keep it few can do that.

A week or so later I saw his truck at the dealer. So, I went in and asked if it was in for service. I was told no, he complains about 14 highway and 9-10 towing and we are trying to figure it out. !!!!!

So, always ask for proof. Or just write it off as justifiable bragging.

BTW, my 95 dodge I kept a log of every gallon anf mileage. i traded it at 105,000. I still have the log book.

It was generally running empty and local driving. The log figures up to about 18mpg over its life!!! With a high of about 23mpg.

Driving style and vehicle says most of it.

I wish my 02 could do that. It is about 2 mpg short.

 

[brods]

The Duramax 6600



“... . the 2500HD/3500 Duramax diesel trucks are producing 17-21 mpg when driven empty and 9-13 mpg while towing. ”



Scroll down for the charts: Diesel Economics and Fuel Mileage, TheDieselPage.com



Along with all the other reasons for fudging, I think people also tend to report their best tank mpg rather than the average. Short fill a tank and you too can get great mpg numbers.

 

[steved]

Its all about ego... and the bigger/faster/more powerful thing... and brand loyalty.

I've had Cummins guys talk mileage with me before and tell me their getting 30+mpg... like I don't know any better.

A lot of mileage claims has to do with your driving style and mods... my truck is stock form wouldn't do much more than 17mpg... and even now, start cruising 75mph and your down into the mid teens.

 

[AClayton]

Its all about ego... and the bigger/faster/more powerful thing... and brand loyalty.



I've had Cummins guys talk mileage with me before and tell me their getting 30+mpg... like I don't know any better.



A lot of mileage claims has to do with your driving style and mods... my truck is stock form wouldn't do much more than 17mpg... and even now, start cruising 75mph and your down into the mid teens.

I agree,most of the mpg figures you hear about are the the best tanks. When I say my MH gets 8. 5mpg..... that was going to Florida at 65mph and very conservative driving. When I go to WVA on my ATV trips pulling a 14' trailer with 3 atv's loaded on,I am lucky to get 7mpg avg. My RV has been modified to achieve about the best mpg one could expect with the usual mods including air intake,exhaust and a programmer to finish things off. When some clown comes up to me and says his RV gets 15mpg towing a rather large sport-ute like a HummerH3,I get suspicious and then angry,because these people must actually think we are stupid to believe such outrageous BS.



I know a diesel RV would render a significant increase in mpg,but when you consider my avg. miles per year at approx. 10K AND the usual $20 to 25K extra price tag for the diesel chassis..... well it doesn't add up for me now. When I retire or have more VAC. time to increase my miles traveled in a year,I will consider the diesel upgraded chassis. I know the 8. 1L is often considered a lemon engine,but so far,I have had no problems with mine in my 5 years of ownership... . other than maybe a quart of oil consumed every 1500 miles or so. As gas engines are not known for next snapping torque,this engine is about as close to a diesel in driveability as you can get... . with the penalty of fuel use of course. And now with the diesel emissions dropping fuel economy down,a gas RV is often closer than you think in fuel savings.



Alan

 

[JUeckert]

Its all about ego... and the bigger/faster/more powerful thing... and brand loyalty.



I've had Cummins guys talk mileage with me before and tell me their getting 30+mpg... like I don't know any better.



A lot of mileage claims has to do with your driving style and mods... my truck is stock form wouldn't do much more than 17mpg... and even now, start cruising 75mph and your down into the mid teens.

very well said! i have been driveing and owning these things since chevy stuck that conversion crap under the hood of them back in 79' or so. started buying them in 81, the conversion crap i spoke of being the first one. it's been my experience that they will get close to each other on mileage when driven the same and speced the same. i have had little to do with the duramax, only friends who own them. early ones report 18/19 on the highway, latter ones 15/16. two things i have noticed on powerstrokes, when the odometer really starts to rack up, they seem to take about a 2mpg hit, same can be said on one's thats seen some bad fuel . i have been told excess injector wear is the culprit . latter model dodge auto's seem to net a gallon or 2 better then ford or gm's. the only dodge i have owned that got better mileage then my fords, was a 90 model with the 3. 07 axle ratio. and the only way it would do so was in low speed situations. i had a chevy with a 3. 42 axle that would trump the dodge, and pulled better.

 

[rbattelle]

Short fill a tank and you too can get great mpg numbers.

I suspect this is the source of many outrageous mileage claims. I once calculated 40 mpg from my truck by short-tanking it.



So of course, now when anyone asks me my fuel mileage I tell them I get 40 mpg empty. :-laf [Just kidding]



Steve - AWESOME with the fuel log!! I wish that would happen to me.



Ryan

 

[Double A]

I've heard mileage claims of the delusional from both Dodge and GM owners. I have both and they get about the same. My Cummins has a 150 hp/400 ft lb advantage on the D-max as well. I average 16. 9 combined highway/city unloaded in the D-max and 15. 9 in the Dodge. Absolute best in the D-max was 19. 6 and in the Dodge 17. 5 both unloaded. I have the 4:10 rear in the Dodge, so that has a lot to do with lower mileage. Towing, the D-max averages 11. 1 and the Dodge is around 10.

I tow a 10K fiver and the GM tows much better than most on this site would think. You don't have to put your foot through the floor to get it rolling, nor does it rev very high to get the load moving. It does down shift occasionally on grades and I wasn't used to that. The only time I ever took the Dodge out of fifth when climbing grades was to slow down:-laf They are both great tow vehicles but they are different animals. If I had to keep one forever though, it would be the Dodge.

 

[tmh1955]

My neighbor has a 2007 CHevy HD with the Duramax, He gets about 18mph hiway, max.

 

[AClayton]

IMO,if the Dodge had an auto trans that was similar to the Allison it would be a much better truck. Of all the mods done to my truck,the single best mod for towing was the TC and Co-Pilot lock-up controller. The Allison locks up its convertor after 2nd gear and the stock Dodge computer locks after OD is shifted into. I can manually lock my convertor in 2nd gear and shift through the gears and what a difference in acceleration vs. the fluid coupling. If I unlock my convertor and try and pull a hill the rpm's rise and puts the Cummins out of its powerband. A diesel is only as good as its transmission backing it.

 

[Double A]

I agree with the transmission comment. My Dodge has the NV4500 so I never had experience towing with an auto until I got the GM. The 6 speed Allison is sweet and I've often wished that I had one attached to the Cummins in my Dodge.

 

[AClayton]

From what I've read,it is not possible to swap an Aison 6spd from a later model Dodge in..... But,an Allison has been swapped in several times over. At $10K ,I doubt I will do it anytime soon. My MH and my Company truck both have the 8. 1L and Allison combo and I have been very pleased with the reliability of both. Members have had very little good to say about the 8. 1 but my RV has 41K and my Verizon truck has 116K... . both are heavy vehicles and driven hard at times with no unusual problems. Both use oil at about 1500 miles to a quart... . told by dealer that this is normal but I don't like it.



My friend hads an 07' LBZ that only averages 14mpg. I told him when he bought it that it would improve..... with 25K on the odometer it hasn't got any better yet!!







Alan

 

[Double A]

I've heard the same about the conversion and the 10K+ pricetag so I never considered actually doing it, just a fantasy. My LBZ has 97K on it and there was a time when the best I could do was 14. 6 combined city/hwy. The mileage has improved over the last two years so there may be hope for your friend's 07. The only thing that I can attribute it to is my driving style, which has mellowed quite a bit over the last year or two.



I've heard claims that the LB7's regularly get 20+ on the highway from other Dmax owners but who knows. 30mpg seems extreme, unless the guy crammed the engine into a 2wd S-10.

 

[BTighe]

my 05 averages 14mpg combined. my 06 cr got 12. towing to the coast is 10-11 with a light 25ft travel trailer. bad road for milage though. best ive gotten is 18 and that was once. got 15 at 75-80 mph on a trip to colorado. truck only towed good after i added about 40hp but aside from milage, i cant complain. trans is 10x better than the 47re. has been a very good truck. for sale in search of another 12v. price is the issue. on a side note, this truck has proved more reliable than every dodge ive owned dispite there weaknesses.