LMM Fuel Economy

[More Power]

GM calls it an "Air Intake Valve", which is controlled by the ECM. The valve is activated during DOC/DPF regeneration, EGR operation and "rich idle".


Jim

[Duramaster]

What did you think of that downturn pipe just ahead of the rear differential?

The C-4500/ C-5500 trucks are the same way. Looks kind of scary!

[DmaxMaverick]

What did you think of that downturn pipe just ahead of the rear differential?

The C-4500/ C-5500 trucks are the same way. Looks kind of scary!

I think GM would rather peel up road stripes than torch pedestrians.....If it ever comes to that.

[More Power]

What did you think of that downturn pipe just ahead of the rear differential?

The C-4500/ C-5500 trucks are the same way. Looks kind of scary!

The pickups use an exhaust tip that exits under the right rear of the rear bumper. Only the chassis cabs (& medium-duty trucks apparently) get the exhaust tip ahead of the rear axle.

I'll have close-up pics of all this in an upcoming article, but the tip exit looks way too close to the right rear shock....

Jim

[jharden1]

DIC average for dealer delivery was 17.4. My LLY was about the same when I first picked it up.

[jsracing6]

i get around 17 empty on highway and 7-9 towing 7000# 28' enclosed car trailer

[Dakster]

I hope to see the 17 mpg empty. I got 15 on the way home tonight from the dealer... 2007 3500 CC Diesel, 4x4 Long Bed, SRW.

[1stDiesel]

I have run 3 tanks of fuel through my new 2007. It is the 2500 crewcab. I filled up today and found I got 14.6 MPG on routine and city driving. I was hoping for better, will it get better? Going camping this weekend will let you all know how that goes pulling my trailer...

[Nolafishr]

I am getting 17.8 MPG on mine, I topped off yesterday at half tank, I had 245 miles on the trip meter and it took 13.7 gals to top it off and I hand calculated the mileage and this is what I got. I did not check it against the DIC, Truck has 400 miles on it so far and still breaking in. I usually fill at half tank because it is a lil easier on the pocket at times, Diesel is at $3.24 a gallon here. I had it on the Highway with most of the mileage before I topped it off to see what it would do. I will keep a check on the Fuel mileage on it, so far I am happy with it.

[denny-o]

mpg for city driving will be all over the place.. I can put you on the loop in DC at 4PM and I guarantee 5mpg at 12mph average...
And a similar story for highway mileage depending on how you drive..
To give some perspective I have a 2007 Silverado 1500 4X4 with the small gas V8... I drive like a little old man
(Wait! I am a little old man, ah jeez, and now we've changed Centurys... Damn I hate it when that happens...)..
I get 16.8 mpg average in mostly rural driving with a bit of village tossed in (1 stop light) and once a week to the big city... You Duramax fellas with your 16 mpg average are doing just fine...
Before that I had a 2004 Silverado 4X4 with the 350 V8 and got - TADAAAA - 16.5 mpg average...
I just bought a new, dealer left over, 2008 Duramax 2500HD CC SB 4X4 and will be pleased if I get 16...

denny-o

[christophersond]

I just returned from a round trip from Cheyenne WY to Ogden UT. I put a total of 997 miles on the truck, and was towing a 5th wheel for a combined weight of 17,970 lbs. I had the transmission in the Tow/Haul mode, and the cruise control set at 75 MPH. Given the fact there are only 7900 miles on the truck, the number of construction zones, and the number of significant grades on I-80 between Cheyenne and Ogden, I am not disappointed with the 8.8 MPG. The ole Duramax just kept on trucking.

[richp]

Hi,

We're in the middle of a trip from Illinois to Pennsylvania and back, towing a 12k fiver.

Hand calculated towing mileage at 55-60 mph (rolling hills, mix of interstate and secondary roads) has been right at 11.4 mpg. Hand calculated mileage tooling around without the trailer (driving between quilt shops and other attractions) for several days was 18.6.

Puzzle -- I have yet to be aware of this truck regenerating -- even when I'm home and driving locally in suburban Chicago for months at a time.

FWIW.

[WyoDutch]

I just took delivery of my '09 Sierra 1-ton xtended cab on Monday. It's still in the break-in period, but mileage is hovering between 18 and 19 at speeds primarily in the 55 to 70 mph range. Average altitude around 5,000 feet here. Heading up and over the Big Horns today... steep grades up to just over 9,000 feet.. will be interesting to see what the average drops to.

Thanks GM and UAW... You make one helluva truck.

My son is getting 22 mpg with his 2004 3/4-T Duramax, but I doubt I'll be able to wring that kind of result out.

[trebin]

I have an 08 CC 3500 Dually 4x4 Duramax/Allison and get 14 driving and 10 towing a 24ft gooseneck. Truck has 10 thousand miles on it. Was hoping for more. Had a 03 2500 LB 4x4 with 245's that got 18.5 driving 80-85 mph. Really would like to see more mpg. The Dually has 17's on it but can't go to bigger tires because the duals would rub.

[ororke1]

I got 19.5 mpg on a recent trip with my 09 Siverado. 6000 miles on it, 68 mph empty. Around 15 local driving.

[nomad03]

I will get 17-18 hiway at 75 with no trailer in tow, if I am pulling ANY trailer from a small utility to my 29 foot rv my mileage will drop to 8-11. I am not very inpressed with my towing mileage. Power is great.

I am running 285/75/16 and have had GM reproram the system, also a K&N air filter, and a supper chip programer. I can set the programer on any setting and it will not effect my mileage.

I have 25k miles on the truck.
is this nomal mileage for this truck?

2007.5 LMM

[richp]

Hi,

A couple of weeks ago, I did Chicago to near Grand Junction, CO, with my '09 LMM.

Actual calculated fuel economy on the last two legs of this trip (topper on truck, cruise control on 65, short stop-off tooling around in Denver), was right at 20 mpg. I know from prior trips that running without the topper costs me about 1.5 mpg on this same route.

FWIW.

[Chevy Boy]

I been using this Excel file for 5 years now with some modifications and it works really good and it's accurate..........been averaging 19.6 mpg on my 2007 Silverado LT 1500 over a 3 years period.

http://www.uklegacy.com/forums/index...e=post&id=2651

[Runaway_Dmax]

I will get 17-18 hiway at 75 with no trailer in tow, if I am pulling ANY trailer from a small utility to my 29 foot rv my mileage will drop to 8-11. I am not very inpressed with my towing mileage. Power is great.

I am running 285/75/16 and have had GM reproram the system, also a K&N air filter, and a supper chip programer. I can set the programer on any setting and it will not effect my mileage.

I have 25k miles on the truck.
is this nomal mileage for this truck?

2007.5 LMM

I do not believe your dealer can adjust a DMax truck to your tire size - the ABS system yes they could, but for speedo - no.

If you still have the DPF in place, your programmer is causing the truck to regenerate more often and will result in lower mileage.

Your K/N filter is a big no-no for diesels. Yes it may allow more air into system, but more dirt as well. There have been independent tests done that show the stock air filter does the best at stopping dirt.

My truck is an 08 CC/long box and its hovers between 18 - 19 mpg and towing my 28 ft fw and atv trailer in tandem 10 - 12 mpg. I hit the magic 20 mpg mark once in the 38K I have owned the truck.

[BMDMAX]

I recently completed a round trip from Atlanta, GA to Loyal, WI to pickup my LB7 race engine from Kennedy Diesel. We burned 105.4 gallons of diesel over 2,137.2 miles for a trip average of 20.27 MPG. The highest leg was 21.0 MPG and the worst segment was 18.8 MPG. All cruise speeds were 73 to 78 with some bursts in the 80's. The 18.8 segment was bumper to bumper rush hour traffic in ATL.

All mileage was hand calculated.

This was with the KD Tow Tune ECM and DPF delete with the KD four-inch exhaust. Everything else is stock on my 2008 LMM. Very happy with the KD tuning on the LMM.

I highly recommend the KD tune for those wanting to bump up their mileage on their LMM.