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Fuel Mileage?

Discussion in '1982-Present GM Diesel' started by Hossbaby50, Mar 19, 2007.

  1. Hossbaby50

    Hossbaby50 3/4 ton status

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    I am thinking about possibly picking up a 6.2L for a work truck to put alot of highway miles on @ 70mph. What kind of mileage can you expect out of a 6.2L with no OD? What I would probably look for is something like this:


    1980-91
    6.2L
    Th400 or SM465
    case is unimportant
    3/4 or 1 ton w/3.42 or 3.73 gears
    singlecab
    4x4
    31-33" tires

    Could this combo net some decent mileage & good reliability? I am thinking of a budget worktruck that will see 50,000 miles a year but still be reliable & get 15+ mpg. I would prefer the manual but I know they are harder to find. The only way I would consider an OD would be a GV or a 4L80E. 700R4 is a no go in my book.

    Harley
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Anything in the range you're looking at should still maintain 16-18 mpg. 3.42's and 33's will do better than 3.73's and 31's...

    FWIW, I just bought CanmoreK5's C1500 with 6.2 and 700R4 with 3.42's and 235-75 R15's. In very twisty, hilly and mountainous terrain I averaged 23.6 mpg over 640 miles. Flatter and straighter highway it should have no trouble breaking the 25 mpg barrier.

    I guess it just depends on how hard you plan on working the truck...for me this is more of a commuter plus house stuff (reno supplies, landscaping crap etc etc)

    My K5 with 4.56's, and 39.5's and the old SM 465 still got me 16.5 mpg on the highway with the 6.2. It was revving at 2600+ rpm which just gets hard to listen to. The ideal rpm for fuel mileage is ~1800 at 65 mph.

    Rene
     
  3. Hossbaby50

    Hossbaby50 3/4 ton status

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    It wouldn't really be worked all that hard except for the heavy mileage I drive. I drive 5000 miles a month typically. It would be required to haul around my work supplies which I am guessing w/tools weighs 800 lbs.

    What kind of motor life can you expect out of a 6.2L? 250K? I am using my CTD right now for this and it is great but my GF is going to need a vehicle soon so I thought I might let her drive the Dodge & I would get a 6.2L worktruck. This would help keep the mileage down on my Dodge since I am still paying it off and it might net me another Chevy.

    Harley
     
  4. rich

    rich 1/2 ton status

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    I have a 1990 6.2 1/2-ton 4WD Burb with 3.42 gears and TH700R4. I average about 18mpg on my 33-inch AT "summer tires", not towing a trailer. I do NOT use overdrive with the 33-inch tires - the truck won't pull it.

    With the 3.42 gears and my 235/75/15 "winter tires", I get about the same mileage when not towing a trailer. I *do* use overdrive when I have these smaller tires installed.

    I'd like to see a little more mpg out of my Burb. It weighs 6000lbs with the small tires (I scaled it). I think my EGR intake hurts me - I need to find time to switch to the non-EGR intake and see what happens.
     
  5. kennyw

    kennyw N9PHW Premium Member

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    I swapped a 6.2L into my '79 K10 as well as converted to 3/4 ton axles with 4.10 gears. Running LT285/75R16 tires (about 33") and no lift I was pulling in 16-18 mpg heavily loaded. But I wasn't able to run 70 mph comfortably. 60 was the fastest I wanted to go because anything more really sounded like I was pushing it too hard. I think 3.73 gears would have been ideal without the OD and helped me run 65-70 more comfortably.
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    300K miles isn't unheard of if the 6.2 is well maintained. My 81 Jimmy has 235K miles on it and still runs strong. the 83 I just picked up has 130K miles on it and also runs very strong. I'd seriously consider something similar to what I just got from Paul. You don't need to tow anything, 800 lbs in the box is NBD and I'm assuming it's mostly highway mileage. Id get over the 700R-4 hatred...or swap in a NV3500 if you must have a manual tranny.

    23-24 mpg is very doable...you just need overdrive to do it.

    Rene
     
  7. Fubeca

    Fubeca 1/2 ton status

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    I've had my C-2500 for just over a year. I don't put many miles on it but I average between 22 and 25mpg.

    My old blazer had 235,000 miles on it when I sold it and the motor was still going strong.
     

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