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Old 03-24-2009, 03:42 PM   #21
KathyandDave
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We're getting about 11mpg (21L/100km)
 
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Old 03-25-2009, 05:10 AM   #22
pvcoach
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I have 130K miles on the Duramax (Crew Cab with 8' bed) and get 11-13 when towing our 06 3400RL, 16-18 around town, and 20-22 on the highway. I keep my speed around 60-62 when towing and around 70 without the Monty.
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Old 03-26-2009, 01:39 AM   #23
happy campers
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We get 11-12 MPG towing, and about 18 without the trailer. But she pulls soooooooooo good. I have the VA SmartBox E and only use it on 70, and only when towing. It keeps the transmission from downshifting out of overdrive except on the steepest or longest grades. That along with not exceeding the speed limit helps with the mileage.
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Old 03-26-2009, 12:49 PM   #24
duffy
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Not to open up another can of worms, have any of you tried after market CHIPS. It made a huge diference for me, it hard to be able to convert our kilometers to your miles. I hate to repeat but it made a huge diference. And yes I agree the tanks are to small.
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Old 03-27-2009, 06:37 AM   #25
Clyde n Deb
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That is another can of worms, and the diccussion usually gets heated if you check the archives. There is quite a difference of opinion when it comes to the subject of programmers voiding warranty, etc. My personal view is I never messed with one because I have been very happy with the performance of my truck as is, and don't wish to have to have the hassle if I ever need warranty work done. Others feel differently...it's their truck and their choice.
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Old 03-27-2009, 03:45 PM   #26
KathyandDave
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We get 11mpg and small change (converting from 21km/100km, to be precise). We installed a giant fuel tank, so no more white-knuckle searches for fuel and we can pass up expensive fuel.
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Old 03-28-2009, 03:29 AM   #27
MIMF
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jimr, My '05 LLY is giving me right at 20 MPG when empty at 65 mph highway. When towing the Challenger at 55 to 62 with tow-haul on and cruise set, it gives me about 13 mpg. But, anything above 62 mpg towing and the mileage goes down the drain. Especially when back in October of '05, I was going thru the Rockies at 65 mph, mileage dropped to 8 or 9 mpg. But, the old boy did the job without missing a beat!

On that trip, the company was paying for my fuel anyway.
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Old 03-28-2009, 04:53 AM   #28
TLightning
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Quote:
quote:Originally posted by duffy

Not to open up another can of worms, have any of you tried after market CHIPS. It made a huge diference for me, it hard to be able to convert our kilometers to your miles. I hate to repeat but it made a huge diference. And yes I agree the tanks are to small.
No, for a number of reasons...have plenty of power and reasonable mileage now, and I do not want to void my 100k warranty.
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Old 03-28-2009, 06:13 AM   #29
SlickWillie
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From what I've seen, Duramax mileage depends on engine series, 4 WD or not, and dually. The early LB7 engines got the best mileage. 4 WD seems to cost a 1 or 2 MPG, and the dual tires about the same.

Programmers; I ain't going there.
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Old 03-28-2009, 10:25 AM   #30
twindman
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My Duramax sucks! I have a 2004 late year model. Yeh, the one that overheats!! That only would be noticed by someone traveling in Az, NM, Nevada or Utah - as it is external temperature sensitive. I am fine under 90 degrees, but at 90 or above and on a long pull up a steep grade as going north out of Phoenix, I have to turn off the AC and it just barely makes it to the top. On the Duramax web site others have the same problem with this engine - only in the Silverados for about a year or so. Oh, yeh, I live in the Phoenix area so have the problem every time I leave home.
ANYWAY, back on topic - I thought I was doing good hauling my 2980 in Illinois where the speed limit is 55 and the highway is level. I got 11.3 or so, I think. One time in AZ/NM with a 30-40 mph head wind I got 7.5 running around 65-70. Around town (probably half on the freeway at 65 mph) I get 16.5 at the best by coasting to stops and starting very gingerly. So I guess my engine is not a very good version.
Oh well......
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Old 03-28-2009, 03:33 PM   #31
Clyde n Deb
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Sorry about your DMax. Apparently you are already familiar with dieselplace.com. If you are, then you know we all don't have the same problem with the same generation of this engine. An actual vote on dieselplace actually proved that the overheaters were far in the minority of the LLY engines. If you haven't already, you may check out a guy on DP that goes by the handle of Texas Christopher or some variation. It depends on whether he has been kicked off again lately or not. He has manufactured several mods for those who have your issues. I do have his CAI on my LLY. I have pulled the mountains of Colorado i the heat you describe with the addition of the high altitude, and have done fine. Good luck with your Montana experience.
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Old 03-29-2009, 02:00 AM   #32
SlickWillie
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Quote:
quote:Originally posted by twindman

My Duramax sucks! I have a 2004 late year model. Yeh, the one that overheats!! That only would be noticed by someone traveling in Az, NM, Nevada or Utah - as it is external temperature sensitive. I am fine under 90 degrees, but at 90 or above and on a long pull up a steep grade as going north out of Phoenix, I have to turn off the AC and it just barely makes it to the top. On the Duramax web site others have the same problem with this engine - only in the Silverados for about a year or so. Oh, yeh, I live in the Phoenix area so have the problem every time I leave home.
ANYWAY, back on topic - I thought I was doing good hauling my 2980 in Illinois where the speed limit is 55 and the highway is level. I got 11.3 or so, I think. One time in AZ/NM with a 30-40 mph head wind I got 7.5 running around 65-70. Around town (probably half on the freeway at 65 mph) I get 16.5 at the best by coasting to stops and starting very gingerly. So I guess my engine is not a very good version.
Oh well......
I don't think it was just the Silverados. I believe my LLY 04 Sierra would do the same in the situation you were describing. I know when I went to the LT 265 tires, my fan was off and on much more when we ran from Ike this past fall. Kind of tells me I'm right at the edge temperature wise. Of course, I don't baby it up a hill either. Not fast, I just like to maintain my speed (around 60-65)
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Old 03-29-2009, 10:18 AM   #33
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I am always intrigued by this topic. Truth of the matter is that we are all going to get what we get, pay for it and move along down the road. There are so many different variables involved in MPG that it isn't even worth discussing. No two people drive alike, no two roads are the same, weather is always different, driver mood is always different, weights are different, tires are different. I guess it makes for good campground chatter though. I get between 10 and 13 towing and 10 and 15 not towing. What really makes me feel better is that I paid $1.99 for diesel at Walmart in Wauchula, FL.
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Old 03-30-2009, 03:07 PM   #34
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I started this topic because I was curious what MPG others were getting and I just switched from a 2000 dodge 2500 with the Cummins to the chevy with the Duramax. I test drove the Duramax on a trip I had taken with the Dodge several times and got significantly less MPG and was concerned. The Dodge got between 12 and 13 consistently. It had a 3.54 rear end with a gear vendors under overdrive and Bully Dog chip. I pulled at 60 to 65 MPH in fourth gear over. The Duramax on the asme trip running 65 MPH got 9+ and with only a 26 gallon tank I was concerned. Pulled from Boise ID to Pasco WA this weekend over three mile hil outside on Ontario OR and Cabbage Hill before Pendelton OR. Had 20 MPH headwinds from Pendelton to Pasco. Drove at 55 to 60 the whole way and go just under 10 MPH. Better but am still concerned about small tank.
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Old 03-31-2009, 12:30 PM   #35
exav8tr
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JimR, The TF OEM tank probably weighs about 20lbs over the original and the extra 19 pounds of fuel would add about 150 lbs extra, not much in my mind. Only you can decide if you want the extra weight verses the extra legs the tank would add.
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Old 03-31-2009, 03:02 PM   #36
jimr
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Phil

I appreciate the heads up on the Tranfer Flow tank. I may consider it this fall. Right now I am on a job that will last until late June or July so not much is going to happen this year. Good thing I get to stay in the Montana and not some hotel/motel room. I like my own bed and the company pays for the space and fuel.

I appreciate everyones comments, seems I may beable to get the milage up to the 10 to 11 range as the engine breaks in more but the 26 gallons is an issue. Good to know there are options.
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