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poor mileage deisel

Discussion in 'Chevy Trucks' started by cut-rite, Jan 6, 2001.

  1. cut-rite

    cut-rite Junior Member
    Messages: 21

    I have a 97 gmc 1 ton dually 4 spd automatic with the 6.5 turbo and 4.10 gears . It has 45000 miles and a 2-3 yard dump body,I am only getting about 9.5 miles to the gallon (highway 25%load before plowing season) I have changed the filters and checked the obvious. Any suguestions? What shoud I be getting? thanks, brad
     
  2. TLS

    TLS PlowSite.com Addict
    Messages: 1,425

    What size tires are you running? This seems low, however the bigger the tire, the less miles traveled and thus less mpg.
     
  3. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Do you have low power?hwta kind of mileage did it used to get?that is a heavy truck and i dont think its all that bad if your foot's in it a lot.My Dad just sold his 94 6.5 turbo ,it was in a shortbox 2wd 94'and had 3.42's.Its best mileage was 15 on the highway,a 350 could get better#'s.
     
  4. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    I have that same truck, and I get around 12-14 mpg depending on the load, and I to have about 45K on it.
    Go to http://www.62-65-dieselpage.com, they are a gm exclusive web site, and someone will know that answer.
    Dino
     
  5. cut-rite

    cut-rite Junior Member
    Messages: 21

    more info- tire size stock 225-75-16 -small for 1 ton .I have only had this truck for 10,000 miles ,mileage has gotten consistently worse from about 12.5 down to present9.5 (same load and conditions). thanks,brad
     
  6. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    we changed to p235/85/16
    It lowers rpms at highway speeds.
    Dino