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Gas mileage

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by drifter333, Jun 7, 2017.

  1. drifter333

    drifter333 Newbie Premium Member

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    I know it's not a Prius but wondering what king of gas mileage some of you are getting? I have a 68 K5 that was getting around 10mpg with 3 speed manual. Swapped out the 3 speed for a 700r4 and now I'm getting...that's right 10mpg. Thanks

    33" tires, 4"lift, 3.73 rear end ZZ5 GM performance crate motor

    IMG_1082.JPG
     
  2. Greg Ducato

    Greg Ducato 1/2 ton status Premium Member

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    My 2005 Suburban Z-71 with 32 inch tires, 3.42 gears 5.3 EFI and 4L60E gets a combined 13.5 MPG and has seen as high as 16.5 MPG on an extended trip at highway speeds. Factoring the Gears, EFI, Engine displacement and improved aerodynamics of this vehicle over yours, I would say you are doing pretty well.
     
    skunked likes this.
  3. Vombrown

    Vombrown Mountain Man Premium Member

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    10 mpg isn't that bad. It's what I would expect with a combo like that.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    I used to be able to squeeze up to 15 mpg out of my '72 K5 years ago,on a 65 mile commute to work,when wind was at my back and I kept my foot out of the secondaries..and there were some pretty steep grades on the route too...this was back when we still had leaded fuel though...(ethanol laced gas doesn't go as far)..
    When I first got it,it had a intake and 2 bbl carb off a 283,I should have left it that way,it pulled stronger at low rpms and was a tad less thirsty with that setup on its 350...it had a Th350 and 3:08's...swapped in a SM465 and if anything,it got less MPG..
     
  5. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    I had a 73. I know different body style.

    It was full time on 35s got 10.

    Part time on 35s got 10

    Part time on 38s got 10.

    You see where this is going.

    Engine was not new but ran good th350 trans. 3.73s with the 35s 4.10 with the 38s.

    Also when I went to 40s and 4.56 it got 10 up to 65. It rapidly dropped off the faster you went
     
  6. drifter333

    drifter333 Newbie Premium Member

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    What would fuel injection do for mpg? I am running a 770 Holley street avenger.
    Thanks
     
  7. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    If your carb is tuned good not much
     
  8. bp71k5

    bp71k5 3/4 ton status Premium Member

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    The tires is what I think kills mileage in these. Every time I changed to larger tires or from AT to MT, mileage dropped a bunch each time.
     
  9. NorCal69

    NorCal69 Professional Nail Bender Premium Member

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    Over 6000 miles on @Greg72 's 496 and I think that I've drank a little less the 5 gallons so far.

    Somebody help me with the math here. ;)
     
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  10. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Must be one of the special 1000 mpg carbs.

    Careful the oil companies have hitmen everywhere
     
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  11. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    See and I have had a different experience. From 35s to 38s it was the same. There were some gearing changes there too that's probably why it didn't change much for me. My rpms didn't change much.

    Even up to 40s as long as I was 65 or under all within a half mpg
     
  12. bp71k5

    bp71k5 3/4 ton status Premium Member

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    Of course if you're already at 10, that may be the bottom. My drops were from ~15 down to about 10. Maybe yours just started at the bottom? :rotfl:
     
  13. diesel4me

    diesel4me 1 ton status Premium Member

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    Those huge tires weigh a ton--I know one guy who had a '71 K20 on 44's when he bought it,it had at least a 6" lift in it too--he came across four 15" 8 lug rims at a swap meet,and bought some 235/75-15's to throw on it to pass inspection (it was too tall to pass the way it was)--we had to grind the calipers a bit to keep them from rubbing the rims..

    After he got a sticker on it he decided to leave those dinky tires on it--said it had much better acceleration and power,and handled a lot better too,no bouncy-shaking feeling on the highway like the big tires had,that felt more like eggs than round...he eventually took the lift kit out and put it back on stock springs ,with 2 extra leafs added up front..said it was like driving a caddilac after that...and his gas mileage went up at least 5 mpg..
     
  14. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    I have also considered this possibility. Lol

    My motor ran great though, in a good state of tune. But I really didn't make small changes so my experience should be taken with that in mind.

    It does seem like a rig should be able to turn in 12 or so
     
  15. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Given how long you've owned it now... I think it's safe to just st call it the "AGLSHM 496" from now on.... :deal:

    -G
     
  16. sponsoredbydad

    sponsoredbydad Dune Slaying Sand Junkie Premium Member GMOTM Winner

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    Hea! How did he get a 68? prototype perhaps O-And I get aprox anywhere from 3 to7 GPM ER...MPG
     
  17. drifter333

    drifter333 Newbie Premium Member

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    Sorry 69. Fat fingered it
     
  18. JoshHefnerX

    JoshHefnerX 1/2 ton status Premium Member

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    I don't have enough miles on this one, but doubt it's much different. My old 77 used to get right around 10. No matter what I was doing.
     
  19. The Griff

    The Griff 1/2 ton status Premium Member

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    These are all things I've either got now, or have been around enough have a solid idea what MPG they tend to get. (Highway numbers)

    86 K5 with a 305 and a 2 BBL with 3.42's and 31's would get 16-17 if I was gentle.
    95 4wd half ton Dodge truck with a 360 and an auto, 265/75R16's and 3.55's would get 15-16 if I was lucky, and with 35's it would be closer to 13-14.
    96 one ton 2wd V10 Dodge truck with 3.55's and 235/80R16's normally would get about 11-12.
    94 one ton 2wd Cummins NV4500 Dodge with 3.55's and 235/80R16's would stay around 19-21
    4wd GMT800 trucks with 5.3's usually were around 13-15
    A late 70's K10 with a high compression 350, an SM465 3.73's and 31's has got anywhere from 7 to 13.
    78 4wd Ford F-250, with a 351M, a 4 speed, and 37's and unknown gears saw 8-9 MPG.
    78 K20 with a 400 and a TH350 with fulltime 4wd, 265/75R16's and 3.73's usually got around 7-8 MPG.
    Tons of 4wd GMT400 trucks with small blocks would see 13-14 with stock size tires, and it would drop to 8-9 with 33's or bigger.
    Anything with a big block, 2wd or 4wd, loaded or unloaded, lifted or stock, 31's or 38's, get's 10 MPG.
     
  20. Lieferson

    Lieferson 12oz Curl Specialist Premium Member

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    Stock suspension 3.73s and 33" tires with a gmgoodwrench crate 350... 10-11 smiles per gallon
     

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