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gas mileage very poor...exhuast pipes???????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Intense Blue, Nov 28, 2002.

  1. Intense Blue

    Intense Blue Registered Member

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    i have 87 k5 with stock 350 fuel injection..33" tires,350 turbo tranny, stock 3.42 gears....drivetrain mainly stock except tranny swap, tires, and dual exhaust. driving the truck nice i get 8 mpg. Runs very strong,always tuned up and taken care of, very well maintained. Can straight dual exhaust with glasspacks cause poor mileage???? I would think with fuel injection i should get 12-15mpg. What can i do????? thanks
     
  2. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Is this on the highway, or around town? I get 11 in town and somewhere around 16-17 on the highway, but I have OD, so that helps.
     
  3. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    welcome to the world of lifted GM trucks. my suburban get about 8 in town and 11 on the highway, i just got used to it.

    /forums/images/graemlins/burb.gif 89 gmc 3/4 ton suburban, 7" lift, 36x12.50-16.5 TSLs.
     
  4. Intense Blue

    Intense Blue Registered Member

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    it's all highway speed and very lite on throttle...8mpg!!!!
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    *psssst*

    Yeah...over here.

    *whispers* fill out yer profile before zakk rips you a new one

    Is the poor mileage recent or has it always sucked? If it used to get good mileage or even just better mileage obviously something has changed. The cat could be on it's way to plugged. The injectors could need cleaning, the timing could be off...

    I know you said it's well tuned but the mileage doesn't agree...

    Rene
     
  6. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I think the deal is the swapped in TH350, no OD hampers mileage.
    Glasspacks shouldn't cause bad mileage, but switching them for Flowmaster Delta flows will help power, sound, and mileage.
    Check your O2 sensor...those things can ruin your mileage.
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Did you bother to correct the speedometer when you went to larger tires?
    Bigger tires and not correcting the speedometer makes the speedometer run slower. /forums/images/graemlins/ooo.gif
     
  8. 90K5

    90K5 1/2 ton status

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    Yeah, if it makes you feel better you are probably really getting about 9-10
     
  9. Wingnutt

    Wingnutt 1/2 ton status

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    That's about for an all around milage. First thing you gotta know, a Blazer is like a baby, when it's hungry all you can do is feed it. Get used to it; it goes downhill from there. /forums/images/graemlins/rolleyes.gif
     
  10. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I get about 10 hwy on my 75 with NO over drive, No lock up converter, Detroit, 4.10's and 35's. I'll know for sure in about a week. I have to do some major repairs on my Supra and will have to DD my 75 for a few day's. I know it's 21.8 miles to work.
    My wifes 79 get's about 12 hwy. it's bone stock no OD no lock up on 31's with 3.73. It gets about 11 on average but had as much as 14 taking it easy to FLA.
     

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