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Chevy Silverado and GMC Sierra Duramax Fuel Mileage

506 messages,  Last post on Nov 30, 2009 at 5:21 PM

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What is this discussion about? Chevrolet Silverado 2500HD, Chevrolet Silverado 3500, GMC Sierra 2500HD, GMC Sierra 3500, Diesel, Fuel Efficiency (MPG), Truck

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#422 of 506 Re: BAD FUEL MILAGE! [dravera] by maddogmurf Aug 10, 2008 (5:12 pm)
Replying to: dravera (Jul 25, 2008 8:41 am) I just had the ECU update put in my 07 sierra, 2500HD, long bed crew cab. Things were all geeked up on the mileage indicator etc after I went from 245 (5ply) to 265 (10 ply) tires. The dealership stated they would not update the computer for the increased tire size.....tough on them at least I will get a few more miles out of the warranty as I'm going to go to 285s real soon, the 10 ply helped immensely with ride under load. I drug a 15,000 lb load 800 miles and got 18 miles to the gallon.....I was sweating as the fuel consumption stated that it was using way more than it was with the new tires.....but the fuel performance is sometimes great, sometimes sux though I have never gotten less than 16 without a lod or 11 with a 15-20,000 lb load.....best time to drive and drag a load is definitely at night when it's cool. In the heat of the day with a head wind it can definitly chow down on the diesel. I've gone from Colorado Springs to KC on 30 gallons of fuel and another time made it to Hayes on 3/4 tank, then from Hayes to Joplin on 2/3 tank and changed nothing except lost the head wind and day went to night.....we'll see how it operates with the new ECU update. I did get a Diablo chip for it but I have to do some tests, like install it properly. The guys who put it in initially didn't follow the instructions.....was not impressed as the truck got noisy with the 80HP boost and acted goofy with the 60HP boost....but bottom line, it wasn't installed properly.....so we shall see.....yea I know about warranty issues and chips......but someone purported better mileage with the chip if you keep your foot out of it. I also found by changing the fuel filter at 50% life and cleaning the K&N at the same time helps as well.....that could be why I got such great mileage with a load on this trip. Even with 26000 miles it runs quieter than any other truck next to it......and ain't had a sports car yet take me off the line. It does ride like a Cadi, run and handle like a porsche, and work like a truck.
#423 of 506 Re: DURAMAX FUEL MILEAGE [gagrice] by maddogmurf Aug 10, 2008 (5:21 pm)
Replying to: gagrice (Sep 19, 2004 2:01 pm) I have gotten as high as 22mpg. Just had an ECU update and got 18 plus MPG over 790 miles with a 15,000 lb load.....go figure.....the mileage is a weird creature on the duramax.....I have gone to replacing the fuel filter at 50% and cleaning the K&N at the same interval......I also change the oil at 100 hours, 3,000 miles or 30% oil life left, which ever comes first. I have noticed better mileage tends to occur with night driving when the temps are cooler.
#424 of 506 07 Duramax by maddogmurf Aug 10, 2008 (5:37 pm)
I bought my 07 in June 07.......I love the truck.....pulls the mountains here in Colorado as though it were on flat ground.   At first the mileage sucked then after about 10000 miles things began to improve.   To date I have gotten as high as 22 on the highway (I-70) doing the speedlimit of 75-65. Never gets above 2000 rpm at 75 mph except when accelerating.   I have had really bad fuel performance with a head wind. I have gotten as little as 11 MPG with a 15-20K load. This last trip though I had at least 15000 on and got 18 MPG after upgrading to 265 10 ply tires and having the dealership install the new ECU updates. I had to keep track of fuel consumption after switching to the 265 tires as the dealership will not update the module for me for the new tire size.   The jake brake works awesome. The thing tows like there is no tomorrow and runs like a sports car, rides like a Cadillac as well.......I bought a Diablo chip and the jury is still out as I found that the guys didn't install the chip correctly. Air bags are a must for big loads.....I wonder just how much it would tow as I have had some loads on it and it just keeps going whether sea level or mountains......   I did find that a new fuel filter at 50% fuel filter life.....cleaning the K&N air filter at the same interval, and changing the oil at 30% life remaining, 3000 miles, or 100hours (whichever comes first) also helps. Long trips go better at night and I'm hoping this last trip with a load is an indicator of future fuel mileage performance. Replies to this message: chevyrich (Nov 22, 2009 6:29 pm)
#425 of 506 Re: 2500HD Slow Acceleration [jwashin] by evanderm Sep 02, 2008 (4:45 pm)
Replying to: jwashin (Sep 24, 2004 6:48 am) Hello my name is Evander, I myself just bought a 01' Duramax and i have the same exact problems... Im Furious i even noticed some blue smoke coming from exhaust and the mechanic said its all due to my fuel injectors. I do not have the $4,000 to fix what they are saying is the prob.So if you find out something new would you please contact me personlly.evandermartinezyahoo.com And theytold me that the extended 7yr warranty expired on 5-11-08 other wise they would warranty it ..
#426 of 506 Bad Mileage. Any suggestions? by jmcgoff Oct 25, 2008 (7:35 pm)
I recently bought a 2007 Silverado Duramax with a utility bed on it. I have been averaging 10 mpg in the city and 15 mpg on the highway not towing anything. Its under warranty but the dealer couldn't find anything wrong. Has any one come across this same problem Replies to this message: jerrydock (Jan 07, 2009 4:36 am)
#427 of 506 Diesel MPG, 2008 2500 Duramax ext cab long box by richardb Jan 06, 2009 (7:53 pm)
10K miles I am getting 16,2 MPG in town driving. Mountain/highway driving getting 17.5 MPG. These numbers should be on an EPA sticker on all trucks for comparison! Trailer towing (27 ft - 8000 LBS) 10-12 Mpg - varied driving. This is a 50% increase in mileage from my Ford 10 cyl with more power. Diesel is currently 25% more where I live. So some savings in fuel.
#428 of 506 Pulled the triger this Dec by losman54 Jan 06, 2009 (9:12 pm)
After many months of researching the next truck I was going to buy, I decided to stay with Duramax and the Allison combination. I needed a truck to be able to tow 16.5K plus and all of the dullies GM, Dodge and forget Ford ( I would get a F450 if you paid me, not with all the troubles that truck is having) I decided to get a GMC Topkick custom built by Monroe Truck Equipment. It has all the bells and whistles...330 PH with a 6 speed trans...I'm getting 14 MPG around town and 17 on the Hwy, which is too bad considering the truck weighs 9,000 plus pounds. The air suspension cab air ride and the air cushion seats are a must, and it came with an 8ft pickup bed. How prefect is that! I love the truck, it turn sharper than a Honda Civic and it's the same length as my old Silverado extended cab. There are several of these truck for sale out there, you just have to look for them...and the people selling them are anxious to make deals, that's if you need tow anything heavier than 16.5K.   I figure that I keep this truck for several years ans then see what GM and or Ford have to offer. Ford will by that time have their act together with the F450 ...they'll have their own engine in the truck and maybe GM is they're still around will put out a production model of 4500 truck in off the line HD pickup.
#429 of 506 Re: Bad Mileage. Any suggestions? [jmcgoff] by jerrydock Jan 07, 2009 (4:36 am)
Replying to: jmcgoff (Oct 25, 2008 7:35 pm) There is nothing wrong with your truck. Some get better mileage than others and some need to get over 20,000 miles on them before they begin to improve. I have over 50,000 on mine now and switching to Amzoil synthetic diesel grade oil helped get another 1-2 mpg. Good luck. Enjoy the truck and stop pestering the dealer; their mechanics don't have a clue anyway.
#430 of 506 Got one! by pete59 Jan 07, 2009 (8:00 pm)
#431 of 506 Got one! by pete59 Jan 07, 2009 (8:13 pm)
My first post was back at #312. I asked about fuel mileage on a long bed two wheel drive diesel with the Allison tranny. Since then I purchased a 2008 Silverado four wheel drive crew cab. I am commuting the 110 miles a day as stated back then. I was hoping to get at least 20mpg to match my old two wheel drive Ford and hopefully better down the road after break in. My commute is about 30 miles of hills and 20 fairly flat. Most days I get right at 20 mpg. Some days a little worse but I have found it seems to make a difference as to the fuel you buy and humidity or rain seems to make a difference also. In the summer I trailed a 16 foot boat behind my 30 foot fifth wheel. On the average ( Interstate ) I got 11.5 mpg. I now have about 20,000 miles so it still early.... I am a moderate driver and stay close to the speed limit. It's amazing how much you watch the instant on-board MPG. and how it effects my driving habits.

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