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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.

View Poll Results: LB7 Duramax local driving fuel economy (55-65 mph)
less than 15 mpg (US gallons) (55-65-mph) 97 7.79%
15-16 mpg 251 20.16%
17-18 mpg 337 27.07%
19-20 or more mpg 376 30.20%
Don't own an LB7 - just interested in the poll data 184 14.78%
Voters: 1245. You may not vote on this poll

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Old 09-13-2009, 07:33 PM
npauli npauli is offline
Join Date: Mar 2008
Location: Peoria, IL
Posts: 80

So...unless new injectors and such would really improve MPG's...I don't see how people get anything significant over 20 MPG Avg. My friends claim to...but they have zero data to support the claims.
It can be done, but not without really working at it.

I've got data over 15k miles with quite a few numbers over 20 (details below). The biggest difference is:
1) the manual tranny gets great efficiency to start with, and enables lots of special techniques to save fuel (like engine braking or the ability to coast in gear for zero fuel use or with the clutch in for minimal driveline drag).
2) I've been paying particular attention to driving for best fuel economy. It takes me longer to get where I'm going, but I burn less fuel on the way. If you saw me drive, you'd probably find the numbers below more believable.

15,697 miles (adding 3% to odo for 265 tires)
699.5 gal (from the pump)
22.4 mpg average
26.2 mpg = best tank
18.5 mpg = worst tank (never got above freezing, some cold starts ~ 0F)
12 months

I got just over 20mpg when I bought the truck in july 2008 (previous owner did too). I probably got 1-2 mpg more from using all synthetic fluids, and the rest is driving techniques.
2002 LB7 2500 CC LB 4x4 80k
6 spd, 3.73, 265's
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Old 09-14-2009, 05:45 AM
NeilLB7's Avatar
NeilLB7 NeilLB7 is offline
Join Date: Dec 2008
Location: Indiana
Posts: 15

I would say that a regular cab manual truck could get better numbers than myself...and things of that nature. Thats understandable. Or even some tunes that are designed to increase economy will help. But I've got people with larger trucks, huge tires, no gearing changes, tuners, etc etc that tell some pretty good tales on fuel mileage.

I'd say that some instantaneous MPG's in my truck are really good considering my average. But again, I can't go by that because I dont drive like that 100% of the time.

My friend likes to brag about what the computer tells him at 60mph on the if thats the average he gets all the time. Yet I tell him that his worst MPG he see's on it is just as valid as the high MPG he sees. When he brags about getting 24MPG...I say he actually only gets 12MPG by the same method. His low is just as valid as the high to me.

We argue, he mumbles something, and we start talking about something else usually.
2002 Chevrolet HD2500 4x4 LT
Extended Cab - Shortbed
Duramax LB7-Allison 1000
Charcoal Metallic Ext/Int
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Old 11-12-2009, 04:24 PM
guss guss is offline
Join Date: Nov 2009
Posts: 1
Default 2004 lb7

I have a diablo program
4 exhaust on the 85 hp setting i can get between 18 to 20 on winter fuel
and as high as 24 in the summer going easy on the throttle
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Old 11-17-2009, 05:55 PM
captcnduit captcnduit is offline
Join Date: Oct 2006
Posts: 1
Default fuel mileage

I have a 2002 2500HD. Bully Dog Power Pup programmer set the extreme setting. I opened up the stock air box, tire pressure at 85psi in 245's.

In 2008, took a 500 mile trip over Thanksgiving. I drove 60mph both ways.....and yes it was horrible but wanted to see what mileage I could get running that speed.

I averaged 25.5 over the 1000 mile trip.

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Old 11-27-2009, 04:50 PM
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BigBlockTank BigBlockTank is offline
Join Date: Feb 2009
Location: Tucson, AZ
Posts: 28

I get about 16-17 MPG on my 6.6 DuraMax with 9850 mi.
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Old 12-03-2009, 08:28 PM
pamax pamax is offline
Join Date: Sep 2001
Location: Northeast, PA 16428
Posts: 5

I have been getting 17 to 19 mpg with 81,583 miles on my 01 crew cab.
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Old 01-27-2010, 12:39 PM
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Centurion6R Centurion6R is offline
Join Date: Dec 2009
Location: Ft. Wainwright, AK
Posts: 33

i've been getting around 18-20mpg with my 01 in roughly -20 degree weather...pretty darned good.
'01 2500HD 4x4 C/C short bed 6.6l "Tessie" Superchips Flashpaq, K&N intake, Exhaust? We don't need no stinkin' exhaust.
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Old 03-17-2011, 04:07 AM
DBradley DBradley is offline
Join Date: Mar 2011
Location: Macon, GA
Posts: 3
Default LB7 fuel mileage

I am a new diesel owner, bought a 2001 GMC K3500 Dually. I have added PPE programmer, S & B cold air kit, and 4" silverline turbo back exhaust. The truck just rolled 100,000 miles on it. I also use Stanadyne performance fuel additive. My mileage increased to around 17 or 18, now all of a sudden can't seem to get any better than 15. Any ideas?
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Old 04-19-2011, 11:56 AM
Driveshaft Driveshaft is offline
Join Date: Feb 2005
Location: Waynesboro, Ms.
Posts: 91
Default to the admin

I Got My Problem Solved And Now Am Able To Login. Thanks.
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Old 04-26-2011, 04:16 PM
ricksofla ricksofla is offline
Join Date: Oct 2010
Location: Ft. Lauderdale, Fl
Posts: 20
Default Ford vs Chev.

2005 Ford E250 van 5.4 liter, 85,000 miles, 11/12 mpg, 2002 Chev. 3500 LT crew cab, 4x4 dually, 317000 miles - 17 / 18 mpg. priceless!!!
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Old 02-26-2013, 04:22 PM
Dustdevil1 Dustdevil1 is offline
Join Date: Feb 2013
Location: Huntington Beach, California
Posts: 18

I often pull a trailer weighing around 10k lbs. Under those conditions, I typically see 10mpg while climbing from sea level to the Mojave Desert (around 2800 ft). 16 mpg on the way home. 13 mpg on flat freeway.

Without the trailer, I see about 16 combined, and about 21 on the highway. But I usually drive past 70 mph. Fuel mileage varies dramatically with rpm on my truck. I would imagine it does with all of them. I have 3.73:1 axles, and it's a 4X4 with oversized tires. I'm sure that has a little something to do with it. Plus, I don't often specifically drive for fuel mileage.
2003 Dmax Crew Cab 4X4 LS
Nicktane 2micron Cat Fuel Filter
A commercial shell and a Trucklocker
That's it.
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Old 09-19-2015, 03:28 AM
Dek Hawkins Dek Hawkins is offline
Join Date: May 2008
Posts: 50
Smile Dek Hawkins

I have a 2500 HD DMAX, 2002, and drive it in England.
I can say it does 27mpg on a 100 mile motorway trip @ 70-80mph,
or 22mpg dodging around.
I know many 4x4 owners who get less from their 2.0L diesels.
I would never swap it. I want a fifth wheel camper to haul, but need to get one from States ??
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Old 11-25-2015, 06:19 PM
Ian7 Ian7 is offline
'04 Silverado 3500
Join Date: Nov 2014
Location: Savannah, GA
Posts: 31

Originally Posted by Dek Hawkins View Post
I have a 2500 HD DMAX, 2002, ... it does 27mpg on a 100 mile motorway trip @ 70-80mph,
Given how far from 'typical' that number is, may I ask if that was a single 100 mile trip and tank top-up when you got there? I guess what I'm saying is that the top-up may have shut off very early and given a false economy?

or maybe a 100 mile long downhill stretch? :-)

(yes I know imperial vs US gallon, still 24+ in our context)
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Old 01-19-2016, 02:50 PM
chessy56 chessy56 is offline
Join Date: Jan 2006
Location: South Milwaukee, WI
Posts: 230
Smile '01 LB7 economy

Without a head wind, running ~57-60mph, mostly empty bed, I'm doing about 22-23 mpg on the highway. Depending on the severity of the head wind, I'm around 19 highway. Most trips are WI to mid IN.

Currently, I'm not getting Chit- truck appears to be down with head gasket issue. 400,700 on the odometer. Sure would like to upgrade to something newer, but a drop in fuel mileage would blow....

What's funny is watching the 50 mile average fuel economy with my Edge monitor plugged into the diagnostic port. Going through Chicago (I-94/I-294 with the sound barriers/trees/buildings blocking most wind), the Edge reported as much as 50 mpg! Bite me! Calculated value and not real, I realize. Still amuzing to watch.
So. Milwaukee, WI
'01 2500HD, LB7, 440K miles
"Stock" engine. Dual fuel filtration system with Kennedy lift pump, BF Goodrich Commercial T/A Traction tires (sold to a dude from Texas- it's living a warmer life just fine down there now!).

'17 2500HD, L5P (Happy Birthday/Merry Christmas to me!!!) Currently bone stock, 90K miles.

"Socialism is a philosophy of failure, the creed of ignorance and
the gospel of envy. Its inherent virtue is the equal sharing of misery."
Winston Churchill
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