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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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  #21  
Old 01-27-2005, 05:02 PM
ibelyea ibelyea is offline
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I have and 02 with "Edge" and never see more than 17.5 solo and 10-12 pulling my 5th wheel. I did go as low as 7.5 in North Dakota, but that was with a 40MPH head wind and 50 MPH. While I would like to get better mileage, I'm a little to heavy footed to really realize any better.
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  #22  
Old 01-28-2005, 11:38 AM
birddriver birddriver is offline
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At 75 on hwy, I am disapponted to see less than 22mpg at 60 I get 24mpg my city average is 17 with 28000 on the clock the only mod is a ventalated air box and a soft toneu cover
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...and they went away praising God.<br />03 DURAMAX/ALI CC LB RED/GRAY LS<br />Ordered 04/03/03 Made 05/29/03 Got 07/05/03<br />1969 CST/10 short/wide 350/400 2wd FOR SALE<br />1997 Grand Prix GT HUD Black(Momma\'s Grocery gettter)<br />1994 30ft. Dutchman RV. TT
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  #23  
Old 01-31-2005, 01:49 PM
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More Power More Power is offline
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I filled up late yesterday. Fuel economy for this tank was 17.8 mpg - winter fuel in January. Pretty typical.....

MP
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  #24  
Old 02-04-2005, 09:31 AM
moondoggie
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Good Day!

birddriver: Are you calculating your mpg from your odometer & the gallons you pump, or from an electronic readout in your cab? If you
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  #25  
Old 02-14-2005, 06:52 AM
moondoggie
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Good Day!

birddriver: Please don't take this truck to your dealer, then get it back & tell us you now get 18 mpg - get it to someone who knows about these things & find out why you're doing so well, if that's possible. Then for those few of us where mpg is more important than snort, we can duplicate whatever you're doing or what's different about your truck.

Blessings!

Brian Johnson, # 5044
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  #26  
Old 02-16-2005, 08:52 AM
PONCH
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Last year (winter) I went on a 6000 mile trip towing my 28.5ft tag loaded at around 9000lb. I drove the northern route to Phoenix, flagstaff and down,then the southern route back to IL
Going out I averaged 70mph coming back was 60mph. This was hand figured at every stop as well as at the end.
Without towing and traveling I run 72 and will get 17.5-18 around town and normal driving I get 18-18.5
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  #27  
Old 02-16-2005, 01:48 PM
DA_MAXX DA_MAXX is offline
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03 d/a, cc, 41K miles. Consistently average 18mpg. Haven't seen anything over 20+. I filler up to the top of the cap everytime and calculate the mileage manually. Daily driver, 38 miles one-way to work, 97% freeway, doing 70mph. No performance mods. Have had 1 injector replaced and 1 allison tranny replaced.
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  #28  
Old 02-20-2005, 01:00 PM
Spartus Spartus is offline
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22mpg Highway @ 80mph.
17.5mpg mixed driving.

14-16mpg towing 6,000lbs @ 75mph.

I tow with Attitude set at level 1. Stock exhaust, stock air box....
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  #29  
Old 02-21-2005, 07:49 AM
Hottruck Hottruck is offline
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Angry

Hey all,
I've never gotten better than 14.5 mpg D/A and I'd like to know what I have to do to improve. I've got about 35,000 miles now..
Thanks for any input...
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  #30  
Old 03-09-2005, 08:29 AM
birddriver birddriver is offline
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SORRY for the long delay in a reply.
A few times I have checked the mileage by hand.
mostly it is of the DIC. Fuel used is always within a 1/10th or so from what I refill to.
I always fill it to the brim so there is no guessing in that.
When I modified the air box I Removed three sides leaving the engine side,bottom and the four corners, also removed the foil patch from the inner finder. Then I smoothed the top and heavly blended the air tube transition and blocked off the little bulb "do-hicky" at the other end.
I use No additives or synthetic oil.
The best I can say is that the LORD has blessed me with a good truck!
Please note: My truck is TWO wheel drive.
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...and they went away praising God.<br />03 DURAMAX/ALI CC LB RED/GRAY LS<br />Ordered 04/03/03 Made 05/29/03 Got 07/05/03<br />1969 CST/10 short/wide 350/400 2wd FOR SALE<br />1997 Grand Prix GT HUD Black(Momma\'s Grocery gettter)<br />1994 30ft. Dutchman RV. TT
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  #31  
Old 03-15-2005, 11:18 AM
jjackson
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Birddriver, can you provide a little more info/detail regarding what you have done to your airbox. i.e., (I smoothed the top and heavly blended the air tube transition and blocked off the little bulb "do-hicky" at the other end)

Thanks, John
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  #32  
Old 03-21-2005, 10:36 AM
MIKE MOG MIKE MOG is offline
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HEY DA_MAXX, WHAY DID YOU HAVE TO HAVE THAT ALLISON REPLACED? [NOISE]?
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  #33  
Old 03-24-2005, 06:00 AM
moondoggie
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Good Day!

Thanks, birddriver. Guessing your airbox work & 2WD are helping lots. Sure wish I had some time to play with my junk
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  #34  
Old 03-24-2005, 08:17 AM
birddriver birddriver is offline
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Using a Dremal tool I removed all the cross hatch support from the top lid and smoothed it. The air tube transition needs to be rounded as much as posible if you cut to much You can use some of the now scrap and a good soldering iron to weld up holes.
((((( Take the MAF sensor out of the air tube BEFORE you begin )))))
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...and they went away praising God.<br />03 DURAMAX/ALI CC LB RED/GRAY LS<br />Ordered 04/03/03 Made 05/29/03 Got 07/05/03<br />1969 CST/10 short/wide 350/400 2wd FOR SALE<br />1997 Grand Prix GT HUD Black(Momma\'s Grocery gettter)<br />1994 30ft. Dutchman RV. TT
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  #35  
Old 03-25-2005, 03:48 AM
MikeT MikeT is offline
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I regularly get 18.6 driving back and forth to work (100 mi per day 60 Hwy/40 City). On the open hwy, the mileage is directly related to speed.
Spd/Mpg
60/24
65/22.6
70/21
75/20.2
80/18

The truck is 100% stock 2002 DA 2500HD CC LB. I run AmsOil 15w-40 synthetic oil and a OEM style K&N air filter.

Mike .T.
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  #36  
Old 03-31-2005, 03:44 PM
gravity420 gravity420 is offline
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Cool

2 years ago I drove from Reno, NV to Anchorage, AK on $232.00 worth of fuel, mainly due to the fact that I only had $240.00 left on me and I was forced to drive this thing like grandma to church. At an average price of I am guessing around $1.50/gal back then divided by 3200 miles or so it comes out to about 20.5 mpg. This is seriously babying it, never acelerating hard from a stop at all and driving at a max of 70mph with the cruise control.

I think that some of you never see over 16-17 mpg because you are as addicted to the right pedal as much as I normally am and enjoy the power and fun that these trucks offer. Those experiencing the high mileage are babying it, never accelerating hard and never drive very fast.

I have also driven about half way thru Canada coming down from Alaska never going under 90 mph and let me tell you I only got about 350 miles per tank. Once I realized how much my speed and acceleration affected mileage I was forced to backoff because at the rate I was going I could not afford the fuel. Then I got up to 600 miles per tank.

So speed and acceleration makes a huge difference. For those of you never getting great mileage, don't feel bad, you are just driving the truck the way it is meant to be driven. There always is a trade-off between mileage bragging rights and having fun, and I suspect that it is way more fun to get worse mileage than it is to drive this truck like a model T just to say how good of mileage you get.

One thing to remember also is sometimes the electronically controlled torque converter slips more than it should, and the truck can feel sluggish and mileage can drop down to the 10-12 mpg range. When this happens, and it happened to me once, if you do the tranny reset sequence, which is going 50+ and shifting to first and bringing it down to a stop 3X in a row it will reset the computer and Voila, the mileage and power is back.
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  #37  
Old 04-08-2005, 11:57 AM
Shorty Shorty is offline
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Thought I would add to the mileage info,just bought used 2002 Silverado C/C D/A.Am getting 18mpg empty hiway,17 around town short trips,Towing 28' Jayco probably around 14-15 thousand gross 11 mpg through Texas and I-40 into NM turned north into 30-40 mph headwind to Alamosa Co. 9mpg. Came across mountains into Grand Junction 12 mpg I would like to do better but am satisfied so far. The D/A will certainly pull,Let the Allison do it's thing,dropped out of overdrive occasionally in the mountains and strong headwinds.Running 60-65 mph Shorty
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  #38  
Old 04-13-2005, 08:48 AM
Jim Brzozowski
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I didn't see anyone mention this so I will. Its not only your rate of acceleration that counts for fuel mileage, its also your rate of deceleration. I suspect that is where a lot of you are loosing out. With these high compression engines if you just jump off the accelerator you are wasting a lot of energy stored in the velocity of the vehicle. You've spent the $$$ to get it up to speed which is where most of the fuel energy is used. It doesn't take much to hold a steady speed. To keep from loosing more fuel mileage decelerating try just backing off a little until you see the speedometer just start to decend. Try to keep the rate of decent in the area of coasting, where you are not using the engine to drag down the vehicle speed quickly but a just supplying enough fuel to keep it at a rate of slow decent. Your best mileage will be when you accelerate and decelerate at a slow rate and cruse at a steady speed for hours at a time, like out in the middle of nowhere. Remember its the rate of change that makes the difference. Food for thought.
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  #39  
Old 04-17-2005, 05:10 AM
Rocinante Rocinante is offline
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Lightbulb

For all of you using chips/programers, remember your truck DIC MPG reads too high when using chips/programers. You have to calculate the MPG the old fashoned way. By the way, the DIC Gallons used display also reads inaccurate, too low, you have to use the pump reading when doing you MPG.
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  #40  
Old 04-19-2005, 08:53 AM
okeehandyman
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I purchased two 05 trucks in nov & dec 04. both are 2500hd 4x4 d/a's one cc & one ext c. I drove each of them kenosha, wi. to florida. they both got 22-23 mpg for the whole trip. now one has 13k miles and one 6k mi. one is avg 16 mpg and the other 17 mpg local driving. when we drive out of town & run steady we see much better mpg, as expected. the secret,i think,is keeping your foot from showing you how much power is under the hood! i carry a lance 915 truck camper sometimes. with that,i get only i5mpg on the highway - but i keep the speed down to 60 to 65.
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