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Old 07-28-2010, 01:24 PM   eBay Motors  #1 (permalink)
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Fuel mileage drop

Hello all I'm new here. I have a 2008 Chevy 3500 HD with the Duramax diesel.
I bought the truck new and off the lot I was getting an average of 400 miles to a tank. I now have 46k miles on the truck and have taken it only to the dealer for service. Some time over the last few months could have been as long as six months my fuel mileage has dropped to 300 miles a tank. This change in mileage happened over night and was not a slow decrease. The truck sounds and runs as good as the day I took it off the lot.

I'm thinking that the dealer flashed my ECM when it went in for service but they claim they have no part in my loss of miles. They also tell me there is no going back to the original programming.

So what do you think, is this possible?

The mileage is bad enough I'm thinking of voiding my warranty and fixing the ECM. I'm figuring that if I got the 400 miles per tank back my fuel savings could buy a new motor if anything went wrong. I've also had bad luck having warranties honored in the past. So I don't know.

Any thoughts.
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Old 07-28-2010, 01:31 PM   eBay Motors  #2 (permalink)
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wow sorry to hear that. and when u get a chance fill out your sig so others can help out better. and where in va do u live
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01 Chevy 2500HD Dmax, 4x4, Reg. Cab Long Bed, SAS Dana 60 HP Kingpin. 10 inches , np 241 x case modded, 400,231 miles on it org. motor
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Old 07-28-2010, 01:31 PM   eBay Motors  #3 (permalink)
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By the way Welcome to the forum, sorry bout that
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01 Chevy 2500HD Dmax, 4x4, Reg. Cab Long Bed, SAS Dana 60 HP Kingpin. 10 inches , np 241 x case modded, 400,231 miles on it org. motor
03 Chevy 2500 HD CCLB. 16x10 Black Bead locks Stock with 271,000 miles
www.GetSomePerformance.com , Dont you think its time you got some!
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Old 07-28-2010, 01:34 PM   eBay Motors  #4 (permalink)
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bad injector(s)?
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Old 07-28-2010, 01:59 PM   eBay Motors  #5 (permalink)
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Do you have larger than stock tires? Tires inflated properly?
Have you cleaned the MAF sensor? ---changed the air filter?
You have the DPF? If so it is possible that it is regenerating a lot, and that uses fuel.


Do you have a long bed-short bed- ? 26 gallon on the short, and 34 on the large.
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Old 07-28-2010, 02:15 PM   eBay Motors  #6 (permalink)
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Thanks for the interest in my problem.
I'm near Christiansburg VA.
As for the truck. It runs and sounds great and pulls the hills around here great even with a trailer loaded so nothing has changed there.
The truck is all stock the only thing new to the truck is a set of front tires and they are the same as the ones that wore out.

The truck is a long bed with crew cab and fuel filters and air filters were taken care at service. I don't know what a DPF is or the MAF sensor is. The tank is the 26 gallon.

I'm taking it to a different dealer next Tuesday. I will give them a shot at fixing my problem.

About a year ago the dealer offered to flash my ECM to accept the northern fuels that I guess is the ethanol diesel. I declined because it said it would effect fuel mileage. I still have that paper around here somewhere with that information on it,

What should I put in my signature?
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Old 07-28-2010, 02:39 PM   eBay Motors  #7 (permalink)
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year, model, mods, even name if you want. kinda show whats done to the truck which in your case its stock. people just want to know what year of truck you are talking about and when it goes to a problem they want to know if you have any mods that could've made a difference
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Old 07-28-2010, 02:47 PM   eBay Motors  #8 (permalink)
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Quote:
Originally Posted by Miss Virginia View Post
....I'm thinking that the dealer flashed my ECM when it went in for service but they claim they have no part in my loss of miles. They also tell me there is no going back to the original programming.

So what do you think, is this possible?

The mileage is bad enough I'm thinking of voiding my warranty and fixing the ECM. I'm figuring that if I got the 400 miles per tank back my fuel savings could buy a new motor if anything went wrong. I've also had bad luck having warranties honored in the past. So I don't know.

Any thoughts.
I got 18.6mpg on my old 08 LMM, took it the dealer for a recall (heated washer fluid). I got the truck back I never saw over 17.0 mpg. I'm pretty sure they flashed it and something changed in the program dramatically
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Old 07-28-2010, 05:13 PM   eBay Motors  #9 (permalink)
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061000 ENGINE AND ENGINE COOLING, ENGINE
Jul 28, 2008 - ECM EEPROM - REPROGRAM ECM. ALL 2007 AND CERTAIN 2008 CHEVEROLET SILVERADO AND EXPRESS AND GMC SIERRA AND SAVANA EQUIPPED WITH 6.6L DURAMAX VA DIESEL (RPO LMM - VIN 6) ENGINE. CSC WAS RECEIVED. *PE UPDATED 5/5/09. CSC LETTER WAS

I found this here
2008 CHEVROLET SILVERADO 3500 TECHNICAL SERVICE BULLETINS

How do I find out the rest of this story?
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Old 07-28-2010, 05:44 PM   eBay Motors  #10 (permalink)
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A crew cab long bed with a 26 gallon tank????
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