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304 Gas Mileage

Discussion in 'Intermediate CJ-5 and CJ-6 Tech' started by heavychevy, Aug 2, 2018.

  1. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    What is a reasonable expectation of gas mileage on a cj5? Mine does about 12mpg on highway. It is the standard 3 speed with 3.54 gears. The tires are 33×12.50x15.

    Anyone have some info. I was thinking about changing to a good bit smaller tire, maybe something on 29 or 30 inches high. Will this help?
    Most of my hardcore wheeling is behind me now.
    Btw it has the motorcraft 2100 carb.
     
    Last edited: Aug 4, 2018
  2. Aug 2, 2018
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Sure it's not 3.73? That's the standard ratio for 1974. 3.54s started in 1976.

    My '73 would get in the low teens in 1973. Are you adjusting the miles for the size of the tires? A 33" tire is 14% larger circumference than the factory 29" (28"?) tire. That would boost your mileage to 13.6 by itself. How fast do you drive? Wind resistance is a might barrier, especially given the aerodynamics of these Jeeps.
     
  3. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Usually drive about 45 to 50 mph. Speedo is off 5 mph according to gps
     
  4. Aug 2, 2018
    heavychevy

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    Danielsville georgia
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    Was just pondering. Many years ago i had a gmc truck with a 350 2 barrel rochester that got 14 mpg. I changed the intake and put a small 4 barrel quadrajet and the mileage went to 17 mpg. Would a small 4 barrel help?
     
    Last edited: Aug 4, 2018
  5. Aug 2, 2018
    Daryl

    Daryl Sponsor Sponsor

    Bonney Lake, WA
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    Any money spent on an intake or carb is very unlikely to ever pay off at a couple miles per gallon difference. The bigger question is how well does it run and would a simple tune-up make more sense to spend the money on.
     
  6. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Runs real good, has the pertronix ignition upgrade.
     
  7. Aug 2, 2018
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    A lot of guys talk about fuel mileage out of a jeep. If I was concerned about mileage I would buy a Hyundai or a Toyota Corolla. It’s a v8. Never going to be an economy vehicle
     
    58 willys likes this.
  8. Aug 2, 2018
    58 willys

    58 willys Sponsor Sponsor

    Millsboro, Delaware
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    13 mpg is about what I am getting out of my '77 304 3 speed running 31"
     
  9. Aug 2, 2018
    heavychevy

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    Danielsville georgia
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    That may be about normal then for 304
     
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  10. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Yes after checking it is 3.73
     
  11. Aug 2, 2018
    Daryl

    Daryl Sponsor Sponsor

    Bonney Lake, WA
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    Anything over 10 would be concidered good.
     
    Twin2 and 58 willys like this.
  12. Aug 2, 2018
    sterlclan

    sterlclan Member Sponsor

    exploring the...
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    I get 14 to 16 running super with tall skinny tires.
     
    heavychevy likes this.
  13. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Yes you are right. I have a s10 blazer that i do most of my running around in. With a 4.3 it gets 19 mpg. Just wanting to see if there was a chance though for improving the cj.
     
    Last edited: Aug 5, 2018
  14. Aug 2, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    That is the feedback that i'm wanting to hear
     
  15. Aug 2, 2018
    sterlclan

    sterlclan Member Sponsor

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    i have block hugger headers and 2 1/2 inch duals out the back a mild cam and the 2100 carb.
     
    heavychevy likes this.
  16. Aug 3, 2018
    Willy

    Willy New Member

    West TN
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    About the Quadrajet mentioned above. They had very small primaries and if working right, did give decent mileage if you kept your foot out of the secondaries. I had a '83 Suburbarn that would get 18-19 on the highway with a Mr Goodwrench 350 and an early Q-jet on a stock manifold and headers.
     
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  17. Aug 3, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Willy, thank you for the reply. I believe that the 304 can do better. It has a bore similar to the 283 sbc. Since i've gotten older the jeep that i have just seems that it is hard to get rid of. We have too many old adventures behind us. Rather than selling, i'm putting it on the highway and using it for small trips.
     
    Last edited: Aug 5, 2018

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