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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ & LMM engine specific topics.

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  #21  
Old 07-05-2007, 11:37 AM
axisrobotics axisrobotics is offline
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I have a new 2007 GMC 2500HD duramax diesel. With 3 tanks of gas and 1,127 miles on the odometer, the computer shows 18.1 mpg. I have manually calculated it to 17.86 mpg.

Mostly short 20 mile runs with some daily city traffic and aprox 125 miles pulling a 3,000# trailer.
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  #22  
Old 07-11-2007, 06:34 PM
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diegojp diegojp is offline
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So what's the secret to all this amazing mileage I am reading about? I am on my 4th tank of fuel and average about 13 mpg city/highway. I drive about 65 on the freeway and my driving is pretty evenly split between city and highway.
Granted I have the 4x4 and usually have to drive with the AC on but I can't imagine those factors make a huge difference. Am I missing something? TIA
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  #23  
Old 07-12-2007, 09:43 AM
Albee Albee is offline
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06 LLY 4X4 Dooley. Best seen on freeway ever is 16.3. Around town, 12-13 mpg. Pulling 17-18K over hill and dale 8-9 mpg. Not as good as my 02 LB7 2500HD. Best was just over 20 hwy. and got around 15-16 in town. This LLY is not near as economical. But she runs good.
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  #24  
Old 07-28-2007, 04:54 AM
axisrobotics axisrobotics is offline
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Location: N. Arkansas Ozarks
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Default re: A/C and fuel mileage

The best I can tell the dual zone a/c stays on all the time. I get about 1.1-1.3 better mileage with the compressor button turned off.
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  #25  
Old 07-31-2007, 12:29 PM
winmck winmck is offline
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3 tanks - mostly highway - averaging 16.5 mpg on the DIC
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  #26  
Old 08-11-2007, 08:47 AM
Sivrug2 Sivrug2 is offline
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Join Date: Aug 2007
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Default LMM mileage

Hi, I am new to forum

I purchased an 2007 LMM six weeks ago and mileage is as 5780 miles-404.1 gal. 14.3 manual calculation DIC says 14.7. I drive mostly highway unloaded and drive like an old granny. 60-65 MPH. Needless to say I am not happy with mileage. I have had diesel PU's since GMC started with the 5.7 and have had Fords, Dodges and GMC's.The Dodge was a fairly good truck but the dealer was very bad so no more Dodges. Currently in my business I have 4 diesels 2001 GMC 2004.5 GMC, 2005 F350 6.0 Powerjoke and the latest 2007.5 and this one is currently the least efficient.
I have the Bully Dog Pup on my desk right now and need to download. I am hoping that this will give me a couple MPG.
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  #27  
Old 08-15-2007, 06:06 PM
SDWA SDWA is offline
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Default I was thinking about new, but...

All this talk makes me want to keep my 2002 LB7, no matter what it costs to keep it running! I've consistently gotten 18-19 mpg from day one, peaked at 21 in the first year, on a full-to-empty flat road trip...

Scott
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  #28  
Old 08-28-2007, 04:30 PM
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diegojp diegojp is offline
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Just thought I would post an update. I did a 5 day offroading trip last week and averaged 9 MPG(DIC and calculated) towing over 14,000# on freeways an mountain roads. Not too shabby, IMO.
Unloaded my truck is still pretty consistantly getting just over 13 MPG with mostly city(60%) driving. Unloaded on the freeway today, I was able to get 19 MPG over about 100 miles at 69 MPH. That dropped down to 14.5 shotrly after I got off the freeway, however.
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  #29  
Old 10-09-2007, 04:45 AM
jharden1 jharden1 is offline
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17.6 DIC on the last 1600 miles. Mixed miles. 7500 miles on the truck.
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  #30  
Old 10-17-2007, 11:11 PM
craigth craigth is offline
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Unhappy 2008 LMM GMC 2500HD Gas Mileage Sucks!

I am VERY unhapp with my LMM 2008 GMC 2500HD Crewcab SWB 4WD gas mileage!! My '02 of the same model got 100 miles to the tank better than the '08! I'm really surprised that 6 model years later and with the fuel price/supply issues that GM could not at least maintain the mileage of my '02 or make it better! I wonder if a power programmer would help?!?!
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