LMM Fuel Economy

[axisrobotics]

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.

[diegojp]

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

[Albee]

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.

[axisrobotics]

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.

[winmck]

3 tanks - mostly highway - averaging 16.5 mpg on the DIC

[Sivrug2]

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.