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Chevy Silverado and GMC Sierra Duramax Fuel Mileage



  • I have about 2200 miles on my new 07 2500HD 4x4, and only averaging around 13 MPG so far. Those are combined in town and highway miles driven at 65 to 75 MPH, and some small trailer towing. It's still increasing at each fuel-up, so I'm hoping it will reach a 17-20 MPG range when it's fully broken in.
  • After seeing your 13 mpg, I don't feel that bad! I also have a Trac-rack ladder rack with extension on my truck and wonder how much that effects mileage. Also how much of an improvement should I see after break in. By the way, how many miles should the break in period be? Good luck with yours....
  • About 100k on a 01 2500HD that I love. Would not start this morning at all.
    Yesterday morning it started and stalled and re-started fine. No other noticable indications prior to this event. Saturday after Thanksgiving, raining in Houston unable to get anybody to have a look until Monday. Any suggestions?
  • I just traded off my 99 2500 gaser for a used 05 2500HD with the Duramax. Can anyone provide some information to this diesel ignorant guy. Everyone says they love their Duramax, but I have a lot to learn. Definite dos and don'ts, things to watch for, fuels and additives, oils, etc. I also hear a lot about chip installation to improve performance and mileage but don't know what to believe. Any recommendations or advice would be greatly appreciated!

    Thanks to all,
    (for the 48 chev I'm rebuilding in my spare time)
  • Hello all....i am new to here but not new to diesel trucks....I have an 06 2500 dsl and think that i am having injector problems but not sure. the fuel mileage has dropped by about 4 mpg and the truck has 32500 miles on it. I was wondering how they figured out to replace your injectors? any info would be appreciated.
  • I have a 2003 Silveraldo Duramax and have recently experienced the not starting and it wasn't the battery or glow plugs. The not starting (it would crank but not turn over). Ended up having the Glow Plug module replaced.
  • rseeborseebo Posts: 12
    I too have an 05 Duramax, but not feeling the love for it. I have heard from other owners and mechanics that the 05 LLY motor is one of the worst that GM has come out with. I have had several problems, Turbo went out, rear seals went out and constant over heating when towing my toy hauler. Same issue, overheating, that all other people I speak to have and am now experiencing my speedometer not working. I have the Banks 6 gun w/speed loader and it and it runs well, just overheats. If you have allot of miles on it, I would suggest running whatever oil they have run. I wouldn't change to a synthetic. I get about 17 - 19 MPG on the HWY at 70 MPH not towing w/285 tires and 10 - 11 towing 10k toyhauler at 60 - 65 MPH.
  • First point to make is that if you look at the LACK of aerodynamics on the front of the truck and the fact that a LOT of air gets to flow under it then you have your answer to lower fuel mileage at 70mph or faster. In my Duramax I can hear the engine start to work harder as I pass through 57-58mph and a significant increase from 65-66 to 70. SO I cruise Interstate at 60-65, usually with cruise at 63-64 and get 22-24mpg depending on conditions. If I slow down on a state highway to 57-58 it goes up to over 25mpg. I DO NOT trust that dam computer and always calculate my own mileage which shows the computer to be off by as much as 5 mpg for city driving and 2-3mpg highway.
    Last point to make is that you have the wrong tires for the transmission programming. If you bought it this way you may need to find out if the computers were recalibrated for a larger tire BUT the largest GM calibrates for on a 3/4 ton is 265 and on a 1 ton 285. The computers CAN be set for your tire size on a 3/4 ton but you will have to find s dealer or other shop that will exceed GM reccomendations. Your problems are the biggest reasons GM did not recomend 285's or larger. I towed 12k travel trailer last year and averaged 12.5mpg on the whole 4000 mile trip but some of it was in mountains where it dropped to 8mpg. In the flatlands at interstate speeds I got 12 to 15 mpg depending on speed. Off the interstates I got 15 to 17 running 50 to 55mph. Pushing the brick that is our truck through the air gets harder over 50 mph.
  • nlccnlcc Posts: 1
    i just bought a 2002 2500HD ext cab 4X4 (227Km)with a Duramax and Allision tranny. Best mileage so far is13 Cdn gal highway empty at 60 mph 280 mile trip...worst was 6 kicking around the ranch and to town empty. New fuel and air filters..Truck is going back to the dealer tommorrow to try and find out whats wrong.
  • I have an 01 2500 HD. First, a fuel additive is very desirable. I haven't been able to tell any difference with the additives found at the grocery store. The better ones come in two types. If you live in a humid environment, one type has additional antifungal treatment. If not, the other type increases cetane (same as gasser octane), injector cleaners, and lubricants. I have not upgraded mine as of yet except replacing the stock filter with a K&N, nice difference. Synthetic oil is a huge overall recommendation. I have studied various chips and it seems that Edge and Banks seem to have the features I would like. I have also read many posts about MPG and determined that the old LBY does a little better. Highway, almost 23 mpg @ 75-85 mph, 11mpg towing a high profile 13.5klbs. I found the gas pedal is really sensitive and using the cruise control or jamming my foot against the X-mission tunnel seems to reduce pedal variance and increase mileage. Intake, exhaust, chip, electric fan are my next upgrades, $$$$.

    Happy Motoring,
  • lnilni Posts: 1
    I have a new 2007 duramax. The indicator lights in the day light mode are so dim, I can't see them. They are fine when its dark.
    I think this is a programmable problem. Have not had the first service yet. Milage is 15.2 average so far. Very pleased with the towing. 7500 lb 5th wheel. Need larger wheels and tires. Any ideas would be appreciated.
  • Hi I am in the market for a new diesel truck and not sure what to get I have had many diiesels in past and have now a 2007 dodge mega cab with 6.7 diesel auto .But always broke down and gets terible mileage. 11 on hwy and 9 in town and 3.9 pulling a 7000 pound trailer. so any feed back would be great also I do have 35 " tires but I drive like an old women to try and improve mileage dont work. please help
  • I have a 2006 3500 crew cab long bed 4x4 with a six inch Fabtech lift and 35/12.50 17 pro-comp x-treme a/t tires. The motor is all stock and i get about 11-12 mpg around town and 10-11 mpg towing a 7000 lb. travel trailer. Never owned a diesel before is this normal gas mileage? Very happy with everything about the truck, even the gas mileage if this is all i can get, because it is a very large truck.
  • nedzelnedzel Posts: 787
    Mythbusters recently did a segment on acetone. They found that it slightly reduced mileage. YMMV.
  • I have a 2004 Silverado 2500 Crew Cab with the duramax. I was running on the interstate at 80 and I was only getting around 14. Is this right? What is the injector problems all about? Truck does not seem to have full power when you punch it, it has better power at 3/4 throttle. Could one of my injectors be faulty and is making me get horrible mpg and power loss? Thanks!
  • Mythbuster didn't used the recommended ratio though. Acetone is still very much speculative but it is interesting that some folks swear by its efficacy.
  • We just purchased a 2005 Chevy Silverado 2500hd diesel. It has the radio controls in the steering wheel. They work fine, but we cannot use the radio on the dash board. We can't change the time, can't use the volume button on the dash, can't program our radio stations. Not sure if we need to tear apart the dash board or what. Any suggestions before we go and do that?
  • KCRamKCRam Mt. Arlington NJPosts: 3,516
    Welcome aboard!

    Since this is not a diesel issue, you'll get a better response asking your question over in the Chevy Silverado and GMC Sierra Audio/Radio discussion.

    kcram - Pickups Host
  • dmax68dmax68 Posts: 1
    I have 2005 gmc 2500 hd crew d-maax. Do you have an 2004 LB7 or 2004.5 LLY?
    If you have an 2004.5 LLY my motor you can do many things. New air box (air in)
    and 4" exhaust (more out) to start. Programmers, I had a Bully Dog Triple Dog got
    17-19 mpg with 130 hp max setting sold it. Now I have a PPE Hot plus 2 E.T.
    avg. 21-23 I've seen 25.8 on long highway trips.

    82k Later
  • starman5starman5 Posts: 1
    I just bought a 2007 Chevy Sierra with the Duramax engine. Can you please explain what is the PPE Hot plus 2E.T., to get the better gas mileage, and where and how I can get it? Thanks
  • nezzy711nezzy711 Posts: 2
    I have a 2003 2500hd duramax that over the last year has been loosing fuel mileage. It has 83,000 mile on it. Just recently 90% of the time when it sits not running for 15 minutes or more it is loosing its pressure prime between the filter and engine. Could this be because of cracked injectors or does anyone have a suggestion.
  • petskamapetskama Posts: 2
    I recently purchased a 2005 Chevy 4x4 crew cab short box, 2500HD duramax, allison tranny. It had 95,000 miles on it. I have put on 7,000 since. I use it for travel, pulling a trailer and hauling. Before running across this site today I was looking for 1 or 2 more used duramax powered trucks for my farm. Now I'm not so sure. I also own a 2002 Chevy HD with the 8.1L gas engine and allison. I always liked the power and the transmission in it - until I bought the duramax! Twice the mileage and definately better torque when pulling a trailer through hills or into winds. 8.1L mileage from 14 at best to 4 at worst. Duramax from 28 at best to 8 at worst. Best conditions were 60mph highway driving for mileage. Worst was 75 mph interstate pulling a 30' gooseneck trailer with a 20,000lb tractor on it. Duramax does have a bullydog performance chip in it. It was in it when I bought it. On a recent trip to Omaha I put on 500 miles with the Duramax. Driving 64mph open highway to Omaha I showed 26.6mpg, after driving in Omaha for 45 minutes it had dropped to 25.3, more highway it was back up to 25.6, and then interstate most of the way back hoe at 79mph the average for the whole trip was 24.5. I did check the display and the speedometer to make sure it was accurate. Short drives around home I average around 19. It looks like maybe I better not count on another duramax matching this one.
  • openend22openend22 Posts: 12
    The LLY's are overheaters.. mine overheats badly..I am considering the lemon law for it..
  • I can say that I have also gotten this kind of mileage with my stock 06' Duramax until they started having nothing but Ultra low sulfur diesel fuel availble in the city. I found that WI has the 500ppm Low sulfur fuel at the pumps and it is less than a 40 mile drive. I fill up the truck every time I am over there visiting my daughter and fill up all the 5 gallon cans I have with me. Mixing this with the ULS fuel has brought the mileage back up for my truck. My other comment would be not to trust that DIC to give you accurate mileage. Mine is usually 2- 5 mpg low with it being closer on highway cruise and less in town. The bully dog chip IS helping you maintain great mileage with the new fuel!
    Alan W.
  • You have something wrong with your diesel!! Mine has never gotten close to overheat even when I was towing 12,000 lbs at 7500 feet of elevation at 80 mph. I have a hard time getting it warm enough for good economy here in MN.
    Alan W.
  • openend22openend22 Posts: 12
    Mine overheats pulling grades when the outside temps are above 70degrees. Its been that way since new, the first time was less then 2000 miles. It now has 20k on it and I leave it parked in the garage for fear of being stranded on the side of the road.. I have had it to dealers 10 times..
  • petskamapetskama Posts: 2
    Your comments remind me of one thing I forgot to mention. I took a local truck mechanics advice and have been using soydiesel in my semi tractors and farm tractors, and now also in my durmax. I do seem to notice better mileage when I'm using it. The mechanic told me that with the mandated change to ultra low sulfur diesel, using the soy blend would help extend diesel engine life (better lubrication of diesel components). I also had a local contractor tell me his skid steer loader runs an hour longer on a tank of soydiesel. The blend that is at the pumps in our area is 2% soy / 98%diesel. It is 2 to 3 cents a gallon higher.
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