View Poll Results: 2004.5 or newer LLY Duramax local driving fuel economy

Voters
1092. You may not vote on this poll
  • less than 15 mpg (US gallons) (55-65-mph)

    454 41.58%
  • 15-16 mpg

    163 14.93%
  • 17-18 mpg

    165 15.11%
  • 19-20 or more mpg

    220 20.15%
  • Don't own an LLY - just wanted to see poll data

    90 8.24%
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Thread: 2004.5+ LLY Duramax Fuel Economy Poll

  1. #61
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Arrow

    daleslad,

    Your engine/fuel system has a problem. A competent and motivated dealer service department is what you need most.

    I would suggest you begin a new topic thread with your comments about engine running issues. It'll get more eyes....

    Jim

  2. #62
    Join Date
    Aug 2005
    Location
    Miami
    Posts
    1

    Post

    2005 GMC Sierra Duramax/Allison. I do almost all city driving and I average about 14.5.

  3. #63
    Join Date
    Jun 2005
    Location
    Marysville, OH
    Posts
    8

    Post

    Originally posted by cruzar:
    You stated that this is the second oil, filter change. Did you change it yourself? if so what filters did you use, I think that someone stated that the oem filters were having problems if so please inform if not direct me to what filters you are using.
    Yes changed it myself both times. Using factory recommended AC filter. Have not seen any posts about issues with it. Only posts I have seen related to the odler style FUEL filter. My D/A CC is 2005.
    Kelly T

  4. #64
    Join Date
    Jul 2005
    Location
    Fort worth
    Posts
    13

    Post

    Thanks, on the looking into the AC oil filter, how about the fuel filter? I have about 3000 miles on the vehicle now and I am monitoring the computer on the oil filter/ fuel filter change.Just looking for some feed back on the filters being used by some on this board.

  5. #65
    rob@rone.ca Guest

    Post

    Has anyone computed the averages for the different models and options ie 2500 or 3500, SRW or DRW, allison or manual, etc???

    I'd be real interested to know other peoples comparison with the 6.5 TD's

    I had a heavy-duty K2500 6.5 TD single cab standard, and used to get 19-20 mpg empty (converted to us gallons)

    With the LLY as below I'm getting 16.5-17 empty in similar driving after 4000 miles on it now.

  6. #66
    Join Date
    Jan 2005
    Location
    Indiana
    Posts
    89

    Thumbs up

    I just got back from a 300 mile round trip that was interstate and some 2 lane highway and got a new best of 21 MPG (calculated). Previous best was ~18.5 MPG. Around town and mixed driving (including some boat towing) I am averaging about 15.5 MPG. I am at almost 10K miles now. Mileage is slowly climbing over time as it continues to break in.
    \'05 Chevy 2500 HD LS CC/LB 4x4 D/A, Century Cap, Line-X Spray on bedliner, SS Nerf Bars, Lund Bug Deflector, 235/85R16E LTX M/S II, Kennedy Custom ECM Tune, Uni-filter, EGT/Pyro & Boost Guages

  7. #67
    Join Date
    Jun 2005
    Location
    Pt Pleasant, WV
    Posts
    18

    Post

    Guys, you have to hear this.

    I knew when it got broken in better it would get better fuel economy, but this past Sunday I really was amazed.

    My mother lives in West Union, WV. I had been visiting her, and was coming home. Two miles from her home, I reset my DIC and thought I'd take my time coming home. It's mostly all 4-lane, but thought I'd put it on cruise @ 55 and see what happened.

    There are several big hills. As I topped the hill behind West Union, it was at 16. However, the farther I came the better it got. By Harrisville it had topped 20, and believe it or not under the I-77 underpass in Parkersburg (55 mi) it was setting 24.2!! I went on south on 77 to Ravenswood, and it was at 24.3!!! However, I sat in a Dairy Queen drive-thru for 10 minutes and it fell 2 mpg. I then drove on to Pt Pleasant and after 120 miles total (the last 30 on two-lane) and 10 minutes idling not moving, it was still back up to 23.6!!!

    I could not believe that holding it down to 55 made that much difference. I have to tell you that I got some mean glances on the interstate, but to get 6 mpg better that at 70, I can put up with it.

    LJ

  8. #68
    Join Date
    Oct 2005
    Location
    fl
    Posts
    9

    Post

    my last duramax was an 01 extended cab short box 2wd and averaged 17-18gph in 14 mile round trip to work with 16 stop lights 19-20gph highway when pulling 11000 lb trailor got 13-14gph all hand figured the duromax i have now is a 04 extended cab short box 4wd same driving as the 01 i get 13-14.5gph city 16-17 highway and 11 pulling the trailor city or highway (i can find all kinds af stuff to beef up the truck and ger worse mileage does anyone know what i can do to improve mileage

  9. #69
    rob@rone.ca Guest

    Post

    Note to LJ

    I had that happen to me once - going 85-90 KMH (= 55 mph) on a road which started uphill, and then went down the rest of the way my DIC was down to 11.5 l/100KM which would be near 20.5 US mpg. (Mine is 05 LLY 3500)

    When I filled the tank, however, the real consumption was nearer 13.8 l/100KM = 17 US mpg.

    The DIC seems to give highly optimistic readings, leaning towards the actual current driving more than the real averages especially when recently reset.

    I'm still hoping for some improvement after a few more KM's on it.

  10. #70
    Join Date
    Jul 2005
    Location
    Otisville , Michigan
    Posts
    2

    Talking

    05 REG CAB WT PACKAGE. 2300 MILES ON TRUCK. CRUISE SET ON 70MPG, MANUALLY CHECKED LAST WEEKEND AND GOT 18.3MPG. ALL HIGHWAY. I GET 14-16 AROUND TOWN. PULLED 4K-5K TRAVEL TRAILER IN SUMMER AND GOT 14-16MPG WITH CRUISE SET@65. MILEAGE SEEMS TO BE GETTING BETTER.

  11. #71
    AndyU Guest

    Post

    Originally posted by AndyU:
    Well, after thorough testing, towing, empty, highway, city, etc, my mileage went down with the Predator. Running empty, I lost about 1.5 mpg in city driving and about the same loss highway. Towing was about the same, maybe even a bit better, but it's hard to tell because of the affects of wind direction, rate of travel, etc which makes it hard to get a good baseline. The Predator caused my DIC to indicate my mileage went way up, but hand calculating my fuel usage revealed that in fact it went down. Very disappointing.

    After restoring the factory program I averaged 19.5 mpg on a 550 mile trip last weekend (empty at 70 mph w/ cruise and a tail wind). I got 22 mpg on the last 100 miles (empty, no wind, 60-65 mpg w/out cruise) after refueling. I think that's pretty good.

    The truck definitely gets better mpg w/out cruise on, letting the truck slow up a bit ascending hills and speed up a bit going down. Also, if I keep it at 65 or less my mpg is much better. Also no hard acceleration.

    I only have 5000 miles. I'm very happy with this truck.
    Quick update. I now have 15,000 trouble free miles on the truck. I added an Edge EZ and I run with synthetic oil. I can now get as high as 24 mpg if I can roll along at 55-60 without any stopping. The norm is more like 22 hwy and 18.5 city, subtract 1 mpg when running with winter blend fuel. The Edge EZ definately gave me at least 1 mpg better, maybe a bit more.

  12. #72
    Join Date
    Aug 2005
    Location
    HUGO, MINNESOTA
    Posts
    126

    Post

    Originally posted by Cliffee:
    I'm averaging 16.5 with mostly short city trips. 1800mi on OD. 2005 LLY
    how fast?
    2007 GMC 2500 crew cab LBZ
    6.6L duramax
    Roof markers and XM radio
    Rhino liner
    Plat series nurf bars
    Putco bed rails
    Truxedo bed cover
    edge juice W/ monitor temp uninstalled.
    Hypertech stage 3

  13. #73
    Join Date
    Aug 2005
    Location
    HUGO, MINNESOTA
    Posts
    126

    Post

    Originally posted by AndyU:
    </font><blockquote>quote:</font><hr />Originally posted by AndyU:
    Well, after thorough testing, towing, empty, highway, city, etc, my mileage went down with the Predator. Running empty, I lost about 1.5 mpg in city driving and about the same loss highway. Towing was about the same, maybe even a bit better, but it's hard to tell because of the affects of wind direction, rate of travel, etc which makes it hard to get a good baseline. The Predator caused my DIC to indicate my mileage went way up, but hand calculating my fuel usage revealed that in fact it went down. Very disappointing.

    After restoring the factory program I averaged 19.5 mpg on a 550 mile trip last weekend (empty at 70 mph w/ cruise and a tail wind). I got 22 mpg on the last 100 miles (empty, no wind, 60-65 mpg w/out cruise) after refueling. I think that's pretty good.

    The truck definitely gets better mpg w/out cruise on, letting the truck slow up a bit ascending hills and speed up a bit going down. Also, if I keep it at 65 or less my mpg is much better. Also no hard acceleration.

    I only have 5000 miles. I'm very happy with this truck.
    Quick update. I now have 15,000 trouble free miles on the truck. I added an Edge EZ and I run with synthetic oil. I can now get as high as 24 mpg if I can roll along at 55-60 without any stopping. The norm is more like 22 hwy and 18.5 city, subtract 1 mpg when running with winter blend fuel. The Edge EZ definately gave me at least 1 mpg better, maybe a bit more. </font>[/QUOTE]What level are u running? I average 15mpg at 70-75. Pulling me 5600# travel trailer at same speeds I get as low as 7.9 as hi as 11, pretty ****ty for such a light load. 6500 miles on
    2007 GMC 2500 crew cab LBZ
    6.6L duramax
    Roof markers and XM radio
    Rhino liner
    Plat series nurf bars
    Putco bed rails
    Truxedo bed cover
    edge juice W/ monitor temp uninstalled.
    Hypertech stage 3

  14. #74
    Join Date
    Oct 2005
    Location
    Louisiana
    Posts
    1

    Post

    Originally posted by eagle in flight:
    My LLY has been getting about 18 mpg all by itself. When I tow a fifth wheel (weight around 14,000 pounds) and travel at 60 mph, I get around 11.5 mpg. Mileage is at 15,000.

  15. #75
    Join Date
    Oct 2005
    Location
    Ely, Nevada
    Posts
    3

    Post

    I am very disappointed in the mileage. I'm seriously considering trading my 05 Duramax in for the new Ford when they come out next year. I have 22k miles and mostly at 75mph on the hiway. The dash readout says 13.9 ave mpg. That's pretty close. The best single trip was 15.9 mpg. Most of my driving is at ~ 5000ft elevation in Northern Nevada. I got the 15.9mpg in California close to sea level. Do you think that indicates something? Please explain to me why there is such a wide range of mpg. It doesn't make sense to me that there can be an 8mpg range for the same vehicle even taking into account different driving styles.

  16. #76
    JohnC Guest

    Post

    Originally posted by omercer:
    Please explain to me why there is such a wide range of mpg. It doesn't make sense to me that there can be an 8mpg range for the same vehicle even taking into account different driving styles.
    Well, I can't answer your question, but I will say that my local driving is pretty rough on mileage. I have a lot of short trips with a lot of up and down hills. I was getting about 13.5 mpg in this cycle with my '95 and I'm getting about 13.5 mpg with my new D-max. The D-max has only about 1000 miles on it and there is the fun factor coupled with the fact that it is a heavier truck, so I'm not complaining.

    Also, my DIC appears to be right on the money. Last fill was 18.3 gallons and the DIC showed 18.1 used. Well within an acceptable margin of error...

  17. #77
    Join Date
    Oct 2005
    Location
    Pensacola, FLorida
    Posts
    7

    Cool

    2500 mile report around town driving without towing:
    1) Stock I got 16 mpg...
    2) Added LDL from FreedomFuel to the fuel and got 17 mpg...
    3) Added Magnaflow 4" turbo-back exhaust and now getting 19 mpg...
    Later this week I add an AFE Stage2 intake and am expecting to hit 20!
    2005 LLY in 2500HD 2WD<br />4\" Magnaflow turbo-back exhaust<br />AFE Stage2 intake<br />Retrax bedcover w/LineX...and the list keeps growing!!!

  18. #78
    JD Diesel Guest

    Post

    Just took a trip to Los wages. There and back got 17.6 Speed most of the time was 76 mph. We is happy. the old 454 sub best was 12mph. JD [img]tongue.gif[/img]

  19. #79
    Join Date
    Mar 2006
    Posts
    16

    Default

    Quick update. I now have 15,000 trouble free miles on the truck. I added an Edge EZ and I run with synthetic oil. I can now get as high as 24 mpg if I can roll along at 55-60 without any stopping. The norm is more like 22 hwy and 18.5 city, subtract 1 mpg when running with winter blend fuel. The Edge EZ definately gave me at least 1 mpg better, maybe a bit more.
    I now have 22K miles on the truck without any trouble. That 23 - 24 mpg at 55 with no wind and no stops, etc has held true, but remember, that's a pretty unrealistic scenario in normal life. I just said it to show an absolute best case scenario. Real world was more like 20 Hwy and 17 city this winter under the best conditions and 2-3 mpg lower when in 4x4 with snow and very cold. Still, I think that's very good.

    Somethings I've done so far that helped improve my economy. (1) Got rid of my lead foot. Seriously, just keeping a real light foot and slower speeds added as much as 2 mpg. Watching the DIC helped me learn to change my habits. That said, the following mods got me another 1+ mpg. (2) Edge EZ running on level one. (3) Boost Stick, but only when combined with the blocking plate and finger stick to bypass the EGR system. Boost stick with a functional EGR had fuel economy go down. the boost stick has helped towing, but doesn't seem to effect my economy empty.

    The mods definately helped my economy towing, adding as much as 2 mpg depending upon conditions. I can get 14-15 pulling my 34' x 8' x 9' goosneck horse trailer (10,000-12,000lb) just going 50 mph on nice back roads w/out starts and stops. Pushing that up to 65-70 drops it down to about 11mpg and pusing up to 75-80 takes it down to about 9. As a rule of thumb, economy seems to drop about 1 mpg for ever 5 mph over 55.

    I will be adding a corsa perfomance exhaust w/ down pipe soon. I'll let you know if that makes any difference after I've had a chance to observe it in action for a while.

  20. #80
    Join Date
    Jan 2005
    Location
    NorthEast
    Posts
    37

    Smile 06 lly mileage

    I have 2500 miles on the 06 and my highest mileage so far is 19.5. I'm really impressed so far. My avg. since new is 17, but keeps getting better. My father has an 05 lly and the best we ever got with that is 17.8.

    I'm really happy with this truck!!!
    2006 Chevy 2500 HD Ext. Cab SB, LLY w/ Alli 6 speed

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