I drive a '07 Silverado 2500HD diesel 4X4 in town I get 17-18 on the hwy 19 - 21. My wife gets in it and hwy is 14- 16 in town I don't know. She gets 16 - 18 in town in her car hwy she gets 18 I drive her car I get 19 - 20 in town and 19- 22 hwy. Some time it it just the driver.

I thought Chevy dropped the 4.10's in the heavy duties once they came out with the 6 speed transmission. All of them i thought were 3.73's now because there was no need for lower gears with an extra gear in the transmission. I might be wrong though.

Nope they still have 4.10 and 3.73. I looked at some the other day. Not sure on the diesels though, too freaking expensive to even think about.

The diesels have only and still only come with 3.73 from chevy. They gas as far as I know come with 3.73 or 4.10. If you are really going to be pullin alot with it 4.10 is the way to go.

matt

My 2011 GMC 2500HD 4x4 crew cab short bed 6.0L gas with 3.73's gets 12 in town and 15 on the highway.

every customer of mine with a 24v cummins gets 20-25 mpg or
better on average.
I'm no diesel performance tech, nor do I own one. But, I know a bunch of 'em & they all tell me that the harder you push a diesel, the more efficient it works.
Have you tried driving the s**t out of it for one tank & seeing what happens?

I believe you can baby them too much, but no way you are going to get better fuel milleage driving it like you stole it.

A diesel may efficiently make more power when you drive it harder because the turbo works harder, but then you are making more power and using more fuel than you need to. 20 is a good round average number for a cummins, 25 is out their one tank in a lifetime except for a couple probably extremely modded trucks with people who know how to drive them.

matt

I'll have to see proof of the 25 mpg. That would be raved about all over the place if that were true. A stock truck getting 25+mpg....meh. Had some relatives driving cummins and the best they ever told me about was 21mpg highway with nothing in the truck except them and the cruise set no higher than 65. They averaged about 17mpg normal every day driving. They were oil field trucks so they romped on them pretty hard. Never even dreamed of 25mpg.

Several years ago I put a Banks power pack on my 2002 Dodge which I had bought new. I was using it to pull a 24' utility trailer and went from good mpg to great mpg.

I've owned 3 Cummins Dodge trucks been watching the Cummins forums for a long time. I've heard a wide range of mileage and seems some trucks get awesome mileage and some just don't.

Seems you got one of the Friday before payday trucks. An aftermarket kit is relatively cheapmay help.
-Brad

Ehh just going to drive it another year and get rid of it. And for the haters out there I have gotten as much as 27mpg on my..........OVERHEAD GAUGE! Everybody knows those things are sooooo accurate on the Dodges, yeah right . Chevys is pretty good, Dodges is just ridiculous inaccurate, but I think it helps sell the truck when you test drive it and see that great number overhead.

Im gonna call BS all day long and twice on Sunday

I have not read the entire post, but I'm betting your truck has an auto tranny. 6spd's tend to get better fuel mileage than auto's.

although its not time yet, it might help your mileage to adjust the valves.

I am not 100% sure if the automotive world can do it, but in the heavy truck world, I can re-flash the software in the ECM with the most current Cummins software available to clear up misc. issues, wich sometimes include fuel economy. You might talk to a TRUSTED dealer and see if they'll reflash the ECM. (it is possible that a software change will clear up the smoke you were talking about also)


what are you driving habbits? do you drive the truck 4 or 5 miles a day and it never warms up, or are you a 60 mile a day driver? if you are the first, not allowing that engine to warm up will cause poor mileage, running around town will do more mharm than good.

What blows my mind is gas has more than tripled in price since 1992 and the mileage in the trucks have gone up at the most 1 or 2 miles per gallon. Makes me wonder if the oil companies have the car makers in their back pockets.

I have a 2007 Sierra 2500HD Z71 Auto Duramax and I get 16-17 in town and 18-20 on the hwy. Towing my 22' Mako Bay with Ttop I get 12-14mpg. 85k miles. I tried various tunes from 1-4 from PPE and it does not change MPG if driving the same way. On Level 3 tune, it seriously jumps up and goes, smokes much less and will drink heavy if I keep stomping it.

Diesels reward you when you are easy on the pedal. I once let my buddy drive it to Houston and he kept it at 65 all the way from Austin and back and it averaged 22mpg. My Audi Q7 TDI 3.0 diesel gets 25mpg/29mpg for me.

A couple of times I thought I was getting really awesome mileage after a fillup until I realized it was the trip mileage I had reset and it was counting up from zero... ; )