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Duramax 6600 Welcome to the Internet's first Duramax 6600 diesel discussion forum for the LB7, LLY, LBZ, LMM, LML, LGH & L5P RPO code engines. Tips on performance, fuel economy, troubleshooting and more.

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Old 03-31-2006, 05:13 AM
tonyskidoo tonyskidoo is offline
Join Date: Dec 2004
Location: Up state NY
Posts: 10
Thumbs up I cant wait

I only have 350 miles on my LBZ and I am getting 13.6, it is a CC 3500 Duelly so I cant complain. But with all the high numbers I am seeing from the other posters I cant wait to see what kind of mpg I am going to get.
2006 4X4 Silverado 6.6l LBZ Crew Cab 3500 Crew Cab Duelly, 17000 miles in 3 months, Black XM, and Siruis Sat Radio (Howard Stern & Bubba rock) Plus Playboy lolol

(sold my) 2001 4X4 Silverado 6.6l Crew Cab Short Box, Juiced with 115000 thousand miles, High Idle sw,

1999 HD Softail Custom, 2004 Skidoo 800-HO RAVE,(sold) 86 Pontiac Fiero 18,000 miles in showroom condition for sale if interested,(sold) 2003 Honda HyBrid to save on the price of fuel 48 MPG
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Old 04-09-2006, 06:56 PM
Texas Bulldog Texas Bulldog is offline
Join Date: Feb 2003
Location: Texas
Posts: 23

I have a little over 800 miles and my first tank by computer was 14.9mpg and by calculator it was 15.5, second tank 15.2 by computer and 15.6 by calculator.
2006 GMC, 3500, Duramax , Allison, Stealth Grey, Westin bars, Gunslinger custom wheels, diamond plate tool box, 16K Reese fifth wheel hitch, GPS, Deep tint, XM, Doran Pressure Pro
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Old 04-18-2006, 02:41 PM
BurnsK BurnsK is offline
Join Date: Dec 2004
Location: Montgomery, TX
Posts: 8

I have 4000 miles with a stock CC dually. It gets better every tankful. My '04 seemed to get just a little bit better (identical truck) but this sure cruises better at high speed. Love the 6th gear. By the way, figure the milage by hand, it actually comes out better than the computer. The computer figures it burned 30 - 32 gallons for an approximate milage of 16 but it only will take 28 - 30 for a milage closer to 17 - 18 mpg. The computer figures it burned more than it actually did.
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Old 04-19-2006, 09:26 AM
kenny kenny is offline
Join Date: Jan 2005
Location: ohio
Posts: 34
Smile lbz mileage

hey guys i got a bone stock lbz (I LOVE IT!!!) im getting about 17
mpg' s city and about 20-21 highway, i just put my goose neck hitch and brake box in it this last weekend ( a b&w turnover ball and a techonisha pilot)
a lot of people say it takes years to get your oney back for the cost of a diesel but in my opioin it is wirth it whenever i need the power to poull a hill with a 4000# tractor on the flat bed, try to do that with a 6.o then tell me how long you think it will take it to be worth it!!
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Old 04-24-2006, 07:20 PM
Matt Robbins Matt Robbins is offline
Join Date: Apr 2006
Posts: 4

My mileage is starting to go up a little. About 16 mpg on the highway according to the computer, about 17 when I calculate it. I've got about 5,500 miles on it so far, I put a set of 295 BFG AT's on it right after I bought it. I only ran two tanks of fuel before I swapped the tires and can't really see that it made a difference in my mileage.

Crew Cab 4x4 SLT - DMAX - Love it.
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Old 05-08-2006, 05:29 PM
hapaschold hapaschold is offline
Join Date: Mar 2000
Location: bayville, new jersey, USA
Posts: 280

1st tank was showing 17.1 as long as i kept her at 70 mph. 75 would drop to 16....

hopefully once broken in, 17 will be norm at 75-80
'12 gmc sierra 2500 dmax slt carbon black.
'12 s350 diesel mb
'10 mazda 6i, for sale
'77 450sl benz, in family since new, sold, still in jersey thou
'91 350sdl benz, 3.5l diesel, 28 mpg
'90 560sel benz
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Old 05-24-2006, 03:34 PM
Dave Dave is offline
Join Date: Apr 2001
Location: Ten Mile, TN
Posts: 180
Default Mpg

Well, my truck just hit 1000 miles. I have been getting 14 or so combined averge. However on the interstate at 75 for a full tanK it was only 13.7 mpg. I hope it goes up at the others did when they broke in.

I hope when I get back from this hitch on the rig to hook a 12000 pound load to it and put some miles on it that way.
2006 GMC SLT K3500 Crew Cab 4X4 Dually, Duramax, Allison.
100th ANNIVERSARY Harley-Davidson FLSTFI with custom Black with blue airbrushed \"Real Fire\" paint set.

Previous Duramax trucks:
2005 GMC SLT K3500 Crew Cab 4x4 Dually, Duramax/allison 25210 miles at trade
2001 Chevy LT C3500 Crew Cab dually, Duramax allison 132,210 miles at trade
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Old 06-14-2006, 09:30 AM
Rippin Rippin is offline
Join Date: May 2006
Location: Bryant Pond
Posts: 1

1st post here. About 2k miles in the first month. Overall average so far is 15.2. Driving is a even mix of rural driving nice and 75-90mph highway. Last tank was 15.6 with a higher percentage of 80-90mph highway. I put 285 tires on and the mileage is with calculated with corrected odometer based on GPS, so fairly accurate.

So far very happy. First GM product in a while, replaces a 2000 f350 PSD which was a great truck also. Getting 1-2mpg better than the PSD and that is with a tight engine still hope to see another 1mpg when I get closer to 10k mileage.

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Old 06-14-2006, 10:49 AM
j7l2 j7l2 is offline
Join Date: Sep 2001
Location: greenwich nj, usa
Posts: 95

I have a 2006 LBZ in a GMC, crew cab, shortbed, 4wd, Allision trans. Bought new in April 2006. I have recored the following mileage:
Tank #1, actual 18.6, DIC says 16.9
Tank #2, actual 19.6, DIC says 17.5
Tank #3, actual 19.8, DIC says 17.6
Tank #4, actual 18.9, DIC says 17.3
Tank #5, actual 18.9, DIC says 17.4

All driving is combination city and highway with AC on, highway speed 65 mph. Truck is 100% stock. Using Stanadyne Performance additive in every tank, 6 oz.

I have asked my Dealer if the DIC is always inaccurate, he says they have found that it varies in every vehicle, some are correct, some are low and some are high on the mileage calculation. I have asked them to contact GM about it. I would think that there must be a calibration adjustment somewhere. If not then the DIC info is of little value in my opinion.

Your comments,
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Old 06-30-2006, 06:57 AM
MillCreekDMAX's Avatar
MillCreekDMAX MillCreekDMAX is offline
Join Date: Apr 2006
Posts: 7

I have 3400 ish miles on my GMC 2500hd cc allison 4wd.

I have been getting around 15 mpg combined. I havent been using any addatives though. that might help my mpg in the future.
06 GMC LBZ - stock for now
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