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Chevy Silverado and GMC Sierra Duramax Fuel Mileage



  • Well my friends in message 215 and 207 the problems you are experiencing are not all linked with GM or the Duramax engine your problem would be with banks. You cant just slap a banks 6 gun on a truck and expect performance without problems or strain on the motor. With this added performance you have to add things elsewhere such as cold air intake, transmission upgrades, exhaust upgrades, etc. If you want the performance without the high temps I suggest going to a smaller chip such as a bully dog power pup or a smaller banks chip.
  • I was now reading your Aug 10, 2008 posting and was wondering if you have a 2007 classic and was the update under a service bulletin? If so do you know the number of the bulletin?

  • I have a 2002 silverado hd. The fuel gauge will show empty and flash low on fuel and then jump to normal but with wrong fuel gauge reading. Any ideas? Was checked and was told replace tank sensor [cost $1000.] I question the diagnosis. Maybe a bad ground?
  • I have a 2004 GMC 2500HD and have 285-75 16 on it and no problems. Looks great and only mod was very slight inner plastic trimming so when I turn there is no rub. Highly recommended. My tire guys at a very reputable shop have done this many times and gave me the idea.
  • I bought my 2005 with over sized tires. They looked good; but they were horrible. I use my truck to travel between my farm and my beach house, a five hour drive. I am finally getting better mileage and a comfortable QUIET ride after replacing the big tires for what the factory called for in a Dunlop 8 ply. You guys who like to "look good" can have all the noisy big crap.
  • The LLY engine has a design flaw in the turbo inlet mouthpiece. There are several ways to fix this, so you should do your own research. If you want the BY FAR easiest, there is a guy in the Phoenix area that has a kit. Send an e-mail to [email protected] and he will be happy to assist. You can also buy the LMZ mouthpiece from GM but you will have to do a little grinding to make it fit. Most folks say they can do that in about an hour (they have all the tools). Your choice. Killerbee (this is his "handle") is an engineer and has documentation on all of his research. HIs kit comes with all hoses, clamps, etc. It is a 15 minute fix. It even includes color pictures. It does not void the warranty, and the parts are warranted against defects for life. The reader's digest version of the problem is that the LLY mouthpiece has a very hard turn and a lot of turbulence is created from this. This heats the air going into the turbo, which heats it more. Result is the clutch fan running much more often sucking HP and causing mileage drops. If you haven't done this already, do your research and replace the mouthpiece using whichever method you choose.
  • Pushing the arrow button only resets the start point for average driving. You get instantaneous mpg for a second or so. It will level back out over time.
  • Did you do this and if so How is mileage and how many miles on truck now. I have 49k on mine and average 10.5 with reg oil
  • Have a 2006 2500 duramax when I pull a heavy trailer I get a chucking sensation in 1 and 2nd but seems to go away after that. Any Ideas. Only when towing. At first thought I had maybe bad belt in tires but I replaced with a little more aggressive and it makes worse feel.
  • I am new to this site and was very interested in purchasing a diesel truck. I have test driven the 09 Dodge 2500, Chevy 2500 and the Ford F250. I only drove the ford because I wanted to compare to the others...(im a chevy guy). There are things that I like about and dislike about all makes. Basically if you had a chevy with a cummins engine and an exhaust brake with power folding and telescoping mirrors, you'd have the perfect truck. But thats not an option, so I was looking for someone to give me a little insight about them. And I am concerned about fuel mileage...again Chevy has the 26 gallon (short bed), and the Dodge has like a 34 gallon on it.

    Can anyone tell me what they are getting loaded and unloaded.....just curious.

  • catamcatam Posts: 331
    I have an 09 2500 CC 4wd LT Duramax/ Allison

    My current mileage stats are as follows:
    Total vehicle miles 6654
    Cummulative average 15.38
    Best tank 19.80
    Worst tank 10.29
    Last tank 17.73

    I tow a triple set up with my boat and a pop up trailer, total towed weight ~ 8500#

    I bought my truck the first week of June this year and used it all summer towing.
    My average towing is between 11-12 MPG depending on driving speed and terrain (I live in Utah so lots of mountains).
    My average when commuting, mostly hwy is 18mpg.
    I haven't done a road trip without towing so can't tell you what that would be. I'd guess right about 20.
  • Thanks...
  • That's about what I get with my 06. I have a camper I pull which weighs about 12,000 lbs and I get 11 +/- . With my 3000lb boat only I get 15 or so.
  • There is a detailed article by Michael Patton about the LLY shortcomings and his solution here (
  • Has anyone had to replace the transmission lines in a Chevy Silverado? I have an 07, 2500 HD. I have heard that this is an on-going problem and after spending $$ to have this fixed, that it could very well happen again.
  • catamcatam Posts: 331
    This was apparently an issue on D/A trucks from 05-07, you may want to go to the website, there are a few threads there that discuss it. I don't know much because my 09 should be unaffected. Good luck
  • My coolant lines were leaking. We had 20" of snow, and used 4x4 to get down the 1/4 farm driveway with difficulty, and went into the house. We had an appointment at the dealer to replace the lines the next morning. When the horn started blaring a half hour later, we went outside and my wonderful 2500 HD Duramax was TOTALLY ablaze and burned completely and totally to a crisp, and all my things with it. Fluid leaked onto hot brake area from horsing through the snow, and BAM! Ever seen a truck like that totally ablaze? Not pretty. To its credit, the gas tank sealed down and never went off. Fire started in the right front engine compartment where the leak was. Insurance paid, I have a new 3500 Duramax now. These lines leak constantly. The Feds are looking into the problem, but it won't help me now. I loved that truck. If those cheap Chinese crimps on the trans coolant lines start leaking DON'T DRIVE IT if you wan tto keep it.
  • What size fuel tank does the 2007 2500HD crew cab short bed have in it ?
  • From the research that I have done....the chevy crew cab 2500 short bed has a 26 gallon fuel tank. The long bed 2500 has a 34 gallon fuel tank. The dodge 2500 crew and mega cab have a 34 gallon tank. Now knowing that of course doing the math on that to get total miles per tank is easy. Getting 18 miles/gallon, youd get approx 470 miles to the tank on the short bed chevy, and approx 612 on the long bed chevy and 2500 crew and mega cab dodges.

    Hope this helps.
  • Yes, I had to have them replaced at about 10,000 miles on the 07 Silverado. Now, the dealer tells me I have to replace them again at 55,000 miles.
  • gm issued an update for those hoses, and they still leak. i have heard estimates of $1200 to replace all 3 lines.

    there is an aftermarket update available at
  • catamcatam Posts: 331
    Where did you hear that estimate????

    All 3 lines are about $100 and maybe 1 hour labor, shouldn't be more than $200 anywhere.
    There is a TSB on these, many dealers will replace them at no cost under the 100K drivetrain warranty as well.
  • Most common problem I see in fuel mileage on these vehicles is that drivers trust the computer to give them accurate mileage. I calculate it based on miles driven and fuel put into the tank at the fill. I stop at the same point each time when filling since it is easy to look in the filler neck. When towing 18,000 + of sailboat and trailer in mountain country I turned 9 to 9.5 mpg. Same rig on the flat prairie gave me 13.5 to 14 mpg. I turned the better mileage when I slowed to 57 mph. When I drive around the cities(Twin Cities, MN) I usually get 21 mpg without any load. Highway mileage is always with some load and gets 23 to 24 mpg depending on headwinds. I find that my '06 Duramax does not like to be driven over 68 mph. I hear the engine working harder and mileage drops to 22 mpg. At 75 mph mileage drops to 19 mpg. The '07 1/5 through '10 Duramax does have somewhat better aerodynamics but that plus is offset by the tuning in the engine so getting over 20 mpg is harder. When I drive back country roads at 55 mph I can exceed 25 mpg unloaded.
  • sm_racersm_racer Posts: 1
    I think many of the milage issues with Diesel trucks are from people moving over from gas powered vehicles. To get decent milage from a Diesel you have to keep the speed way down ie. less than 70 and get used to crawling away from stop lights.

    I was totally disapointed when I moved from a 2006 Tacoma that was getting 17 city and 23 hwy to my 2009 Silverado Crew Duramax. If I drive the truck like any other vehicle or my previous truck I get 14-15 city and 16-17 hwy. The best I can get out of my 2009 while milking the [non-permissible content removed] out of it and pissing everyone off around me is 16.5 city.

    Previous truck was able to tow and get 12 while the new chevy gets 9.5? Gone are the days I could tow at 75 or 80 as well.

    I think many of the claims here are exagerated or from older trucks with out the DPF system.
  • andeyhallandeyhall Posts: 1
    I'm just looking on here to try and find out mileage for 6.6 duramaxes for my dad....he's thinking about getting an '04. I'm a powerstroke guy myself. I'm not here to start anything about that, I just noticed you have an Edge tuner. I'm definately not a know-it-all when it comes to diesels, but I stay in Powerstroke forums A LOT! I've done a ton of research on tuners as I am looking to get one myself. From what I have read so far, Edge tuners are simply trash. They do not tune the transmission, which is not good for your truck at all, and from what the guys tell me also, canned tunes (pre-loaded tunes) are not good for you truck either. Most everyone recommends SCT with custom tunes. Just thought I'd pass my research on. Again, not trying to start anthing.
  • jerrydockjerrydock Posts: 29
    One of the joys from driving a diesel is being able to "smoke out" the jerk who tosses his cigarette butt out his/her window. I get next to them and nail the pedal; works wonders.
  • kacansas06kacansas06 Posts: 33
    The tailgater who is trying to get your truck to run 10-15 mph over the speed limit on a city street because his rice burner can't accelerate if he slows down. The he follows me onto the ramp for the interstate, I floor it and a 1/4 mile later at 65 mph(speed limit) I look back and he is just finding his way through the smoke. Somehow I get a lot of room around me for awhile.
  • kacansas06kacansas06 Posts: 33
    As I have said on the and so have many others it is all in the way you drive. I do not try to cruise my 6.6 diesel at 80 mph because it guzzells fuel at 17 to 18 mpg. However if I run 65 to 70 I get 20 to 22 and running on slower highways at 55 to 60 I get 24 to 25. City mileage is 19 to 21.
  • byurunrbyurunr Posts: 1
    I'm new here and have been reading some of your posts. This the first I've heard of "leaking trans lines" (Post 513 is Scary). I've NEVER had a leak, period.. I am @ 118,760 for miles, fourth set of tires, third set of front shocks, second set of front hubs (305-70-16s). Tire "noise" post, had that, tires had "cupped" causing very rough ride and plenty of noise. Changed to less aggresive tread but still same size. Cupping primarily caused by lousy alignment(s). Mileage, have to agree with various posts RE: Leadfoot, giulty myself, from rice burners to mustangs ALL have that same confused look when they see your back bumper pulling away.
  • artgpoartgpo Posts: 483
    I am getting 20 mpg on the highway at a steady 72 mph and between 11 - 12 mpg towing my 11, 800 lb 5th wheel. Mine is a 2009 2500HD Crew Cab, long bed with the Duramax/Allison powertrain. These are real mpg results using a calculator and not the Driver Information Center, however, the DIC is very close to the calculated results.
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