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Chevy Silverado and GMC Sierra Duramax Diesel Questions



  • I have a '07 DuraMax Diesel and only get around 14MPG. I think that is very low. I just turned 45,000 miles. I drive senseably; not hard on the gas pedal. What kind of mileage are the rest of you getting.
  • My '04 Duramax (chipped w/Edge and K&N filter system) gets 21-22 mpg at 65-70 mph. At 75-80 mpg mileage is 18-19 mpg. Although it's been chipped I believe the mileage improvement is no more than an estimated 2 mpg. The vehicle has 72,000 miles on it and I live at 900 ft. above sea level on geneally flat terrain. I do believe your mileage is unusually low.
  • I live in SD and around here it is mostly flat also and our elevation is not very high either. I have taken it in to the dealer and all they asked is "any warning lights on" and I said "no" and they said then the truck is running fine. There is nothing wrong or some light would be coming on. I have talked to other truck owners and they say they have been getting much better mileage than I have been getting. Don't know why????
  • bones417bones417 Posts: 6
    edited November 2010
    OK let's make sure we are talking apples to apples. Is your 14 mpg your average overall or is that highway mileage? I have an 07 classic 3500 my average overall highway and city is 13 mpg but if I get on the interstate hold it below 65 I can get 22 mpg. I think 13 average isn't bad this isn't a small truck, I didn't get the Duramax for mileage I got it because it can pull my fifth wheel trailer. I live in Utah at about 4200 feet and nothing is flat.

    Also it seems to me that most people I talk to about fuel mileage seem to stretch it a bit(maybe trying to justify paying the extra for the diesel). I say this because some that I have talked to that claim far better mileage than I get, when we go on trips pulling similar loads when we do stop for fuel we are within 1 or 2 gallons of each other in fuel used, they should have used far less than I did since they get much better mileage. I don't know maybe it's the new math.
  • fredenfreden Posts: 3
    edited November 2010
    You bought too new of a Duramax to get any better fuel mileage than the earlier LLY or LBZ engines. The 07 classic down to the 06 engines were the best for mileage, and 310-360 H.P.. The new LMM with 390 HP are not as good. I have owned many of both.
    One ton truck with pulling power and respectable fuel mileage is a lot better than FORDS same if not worse mileage, if you can get out of your rental car enough to drive it or the earlier 6.0 they had in 04, where you kept looking for the "power" switch.
    I get 14 mpg city in my 08(programmed to 500 hp) and about 22 hwy. My last 05 got 18 city & 24 hwy. Like the new one better, and I can make a 5L GT mustang look stupid!
    The 8th digit in your v.i.n. tells you if you have the fuel saving #2" LLY #D"LBZ if it's a 6
    it is the same as mine LMM 390 H.P. A LITTLE TOUGH ON FUEL,BUT THE BEST TRUCK ON THE ROAD!
  • folbfolb Posts: 54
    I have an 05 2500 with tool boxes. I have a PPE power adder programmer that plugs into the OBD II and on average I get 19.8. If I really watch my lead foot and go hiway, I've gotten 29. Seriously.
  • I have an 07 classic LBZ - 4 x 4 20 K miles on it bone stock. I get an average of 13.9 in town and 17.8 on the hwy. Everyone is talking fuel mileage on there dura max. One guy gets 14 mpg another 20. But the question should be comparing apples to apples, who has 2 wheel drive, and who has 4 wheel drive???????? :shades:
  • folbfolb Posts: 54
    2005 duramax 4x4 town and highway normally about 20.5. I have the PPE power adder. setting 3 of 10. Better air/fuel mix I guess. Gotten 29 before on a 1 1/2 hr drive to DC.
  • I have an '04 3500 GMC crew-cab and long bed (8'). Everything is stock but I use synthetic oil. On my best day, I can get 14-15 mpg combined driving and 17.5 highway. I plan on installing a cold air intake and 4" exhaust with a Bulldog programmer in the near future. I love the power I have when pulling our 36' fifthwheel RV and the comfort of the ride. When pulling my fifthwheel, I average around 10 mpg, so long as I keep it between 55 and 60 mph.
  • folbfolb Posts: 54
    I have a Bullydog I'll sell you. I wasn't impressed. I got the PPE. It has 10 settings. I keep it on #3 and have gotten 29 MPG. 2005 crew cab with tool boxes.8' bed.Duramax and single 4" I think, exhaust.
  • I just bought a 07 3500 crewcab dually in Dallas and took it to Toronto Ontario and got 22mph on the highway doing 75 on cruise.
  • My 05' has116000 and runs great.
    but my last trip,I kept it under 70mph the whole time and got less than 17mpg. The truck is stock from the day I bought it brand new. I would expect worse mileage when I have my tools in the truck,but this trip the truck was empty. If I wentv with a chip,what kind of problems or damage to my truck should I expect? anybody?
  • folbfolb Posts: 54
    My 05 has 93k. I have the Pacific Performance Engineering(PPE) OBD II programmer. I keep it on tune 3 out of 10. Seems the faster I go, the better mileage I get. 29 MPH on an hour and a half trip to DC. I changed the fuel rail valve to a PPE valve. I have experienced a trans problem because of too much power which puts too much pressure in the tranny lines. Bullydog and PPE have kits to put in the trans to prevent this but I haven't done that. I really only had trouble when towing thru the mountains. Easy to reset with the programmer though.
  • I am having this same problem. What was your fix?
  • barrailbarrail Posts: 27
    Here is my two cents, I have (diesel domination's ) duramileage ez tyuner . I've only experimented with the lowest ,2nd lowest and 2nd highest settings so far, and I haven't noticed much difference in mileage yet. I'm running a 6'-8' bed full of hand tools but not towing with it . all the settings seem to all but eliminate turbo lag but the weather has been to cold to get any decent mileage. So far, transmission seems to be working fine. Hope this helps in somesmall way.
  • gmcustsvcgmcustsvc Posts: 4,250
    Have you resolved the issues with your vehicle?
    GM Customer Service
  • Christina,

    GMC only wants to pay half to get my truck fixed. It will still cost me 2k-2.5K to get fixed!!! The truck only has 80K on it, GMC should pick up all the cost!!! I don't have 2K to fix the truck right now! This sucks!!!!!!

    Can you get me Dan Downings phone #? I would like to talk to him, my so called district specialist Jerrod at ext. 11060 is not so helpfull!!!

  • cls3cls3 Posts: 1
    Hello, Could someone give me some advice? I have ordered a 2011, shortbed duramax 4x4,crew c. I've been reading the posts about chips and realize that that's probably my best bet. I plan on pulling a 32 ft. 5th wheel but still will be doing every day driving without the 5th wheel. I'm concerned about effecting my warranty, creating trans. issues and selecting the correct chip/exhaust. Any suggestions would be appreciated. Thanks, CLS3
  • My truck is stock, can't help on the chip part.

    My advice would be not to buy the Duramax unless you want to change out your head gaskets at 80K miles! If you do buy get the extended waranty!!! Diesels are very expensive to fix!!!! Replace head gaskets 3.5K-4.5K to fix!

    As you can tell I'm not to happy with GMC right now! It is the end of February I have been dealing with this since the 1st of the year. It's been 2 months and I am finally suppose to ge my truck back today!!!!

    Good luck!!!!!
  • folbfolb Posts: 54
    I have a 2005 and love it. I put a PPE programmer on mine. It plugs into your OBD II reader. Nice thing about that is unlike a Banks system which is installed under the hood with lots of wires and such, you can unprogram it to take it in for service. My tranny can't take all the power though. Can only go to 3 out of 10. Better gas mileage too. PPE, ATS and Bullydog all sell some tranny upgrades for the slip issue under too much power. Haven't gotten mine yet tho.
  • I to have an 05' d-max and love it. It has been a stock truck up until 116,000 when I put a diesel domination programmer in it. The programmer offers options like trouble shooting engine codes, different tire size reprogramming, and its simple to install. If the truck has to go in for warranty, you reset the trucks settings back to stock. I have close to 4000 mi. with the programmer and, with the weather starting to warm up, I 'm starting to see my mileage improve slightly. Hope you have as much good luck with yours as I have.
  • buy it, take care of it, don't add a thing to it(after market), love it. The best truck I have ever owned. My 2008 diesel 6.0 4x4 3/4ton Sierra has been flawless in power and I pull a 25ft trailer in steep terrain with no problems. I've had some minor issues which were dealt with thru warranty.
    I would not add a thing to the motor or exhaust, for warranty reasons but also because it simply does not need it.
  • Leave it the way it comes! I have a 2007 Classic 3500 crew cab and I pull a 35ft fifth wheel in the mountains of Utah and Idaho. It comes stock with all the power you need you can pull your trailer faster than any one should on the flats uphill it doesn't matter. I know several people that have chiped there trucks and yes they do get power gains but all those full mileage increases that are written about on this and other sites I havn't found anyone that has actually gotten more than a few miles pre gallon gain. You can't drive yout truck far enough to ever offset the cost. Maybe that's why it seems some people over state the gains they have gotten.
    I love this truck I have just over 60,000 miles and no problems.
  • gmcustsvcgmcustsvc Posts: 4,250
    Please keep me updated on your situation.
    GM Customer Service
  • gmcustsvcgmcustsvc Posts: 4,250
    I'm happy to hear of your satisfaction with your truck. Please feel free to contact me if you have any questions, comments, or concerns.
    GM Customer Service
  • Christina,

    Got my truck back 2 weeks ago from the dealer (after they pulled the heads and sent them off to the machine shop and put it all back together). Drove it 10 miles to my work from the dealer and when I got to my work coolant was spewing all over the place. Had a flat bed truck come pick my truck up, couple of days later dealer calls me back saying it needs a new cylinder head. Waited a week for new cylinder head, dealer starts putting engine back together and calls me and says it needs new exaust valves in a couple of cylinders. Was told last week that I should get my truck back this week. I have been dealing with this since the end of December. The truck barely has 80k miles on it. The duramax diesel engine is a piece of crap!!!!!!!!!!!!!!!

  • barrailbarrail Posts: 27
    Slayersmith; sorry to hear your trucks giving you so much trouble. Besides myself, four of my friends have D-max's and have had very few problems. One 05' with the LLY has 350,000 with the original brakes on it. another 05' has 200,000 , but the chicago weather destroyed the fuel lines. that was a frame off to repair it. mine has a 121,000 with only regular maintaince. hope you get to the bottom of the problem. Does the repair shop work on D-max's very often? good luck.
  • Barail,

    My truck is an O3. I loved this truck before all the problems. The 80K miles I have on it are all long distance road miles on weekend trips. It's a good lookin truck. It's sits with a cover on it in my driveway during the week. I was told when I bought this truck that the engine would break in at 100K. Very disapointed with this truck.

    You might want to check out getting extended waranty, if you have to do any major work to the engine it is very expensive. Blown head gasket on the duramax is a 34 hour job at $100 per hour, you know what I'm saying! Thats just labor, parts are another 12 to 15 hundred bucks.

    I am lucky, I have a beater that I drive for work, If I did'nt, wonder how much a rental car would have been. Truck has been down now for 2.5 months at 40.00 per day = Doh!!!!!!!!

    Duramax = FAIL!!!!!!!
  • dixmaxdixmax Posts: 1
    Our 02 'Max" has 97k miles, mostly long distance. No internal problems
    'yet'. Wonder if a chip would be an option for better mileage and power at this point.
    I don't have the readout computer, but I keep exact "per mile", "per tank" records. I get 9-10MPG with 12k trailer, 17-18MPH solo around town.
    Anyone had any experience with the new 2011 "DEF" system? Reluctant to buy it.
  • gmcustsvcgmcustsvc Posts: 4,250

    My name is Michelle, I am assist Christina at this time. I have read over your correspondence with Christina. I can understand the frustration that you are going through with your situation.

    We would like to set up a case for you. Please, e-mail us the following information:
    -Your first and last name.
    -Your completely contact information and the best time for us to contact you.
    -The VIN of your truck
    -The current mileage that is on your truck
    -The name and location of the dealership that you have had the to for this issue

    Once we receive this information we will be able to set up a case.

    Michelle P., GM Customer Service (assisting Christina)
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