1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Shocking MPG

Discussion in 'Early CJ5 and CJ6 Tech' started by 52m38, Jan 15, 2009.

  1. Jan 15, 2009
    52m38

    52m38 Same jeep since 1980

    Cody WY
    Joined:
    Jul 29, 2008
    Messages:
    94
    hey guys
    My rebuild is running great.
    Shocking mpg though we are talking 8 to 9
    all short trips and its pretty cold..
    tires are aired up.I might have been getting that on my blowd up motor
    You guys have any experience with the mileage getting better when they get broke in more..
    I'm at a 100 miles or so
    zero smoke of any color
    does't miss
    fires on 1st chug
    havent put the HEI in yet
    Brakes cant be draggin,,They dont work to good when you smash on um
     
  2. Jan 15, 2009
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    4,641
    Check your plugs and make sure your not running rich - if it's a new build, yes, I have had them get much better after about 1K in miles. Be sure to follow proper breakin procedure.
     
  3. Jan 15, 2009
    52m38

    52m38 Same jeep since 1980

    Cody WY
    Joined:
    Jul 29, 2008
    Messages:
    94
    Ive checked one on each side. both looked good. Break in is going good. getting used to the 420 is odd. thanks for the info though it runs so good I cant believe mileage is that bad..

    I have an idea but i think its a new post so we will see..
     
  4. Jan 15, 2009
    jeep2003

    jeep2003 Well-Known Member

    Vestal NY
    Joined:
    May 30, 2006
    Messages:
    1,526
    a hundred miles doesnt seem like enough to get an acurate reading
     
  5. Jan 15, 2009
    52m38

    52m38 Same jeep since 1980

    Cody WY
    Joined:
    Jul 29, 2008
    Messages:
    94
    thanks for the ray of hope
     
  6. Jan 15, 2009
    Wmi68CJ5

    Wmi68CJ5 Let the Sun Shine!

    Twin Lake MI
    Joined:
    Aug 10, 2006
    Messages:
    486
    is you speedo reading right? running bigger tires than stock will turn odometer a little less. The brain trust here could probably figure it out for you if this is the case.
     
  7. Jan 15, 2009
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member

    Portland Tn.
    Joined:
    Sep 20, 2002
    Messages:
    3,631
    x2
     
  8. Jan 15, 2009
    marc

    marc New Member

    sacramento
    Joined:
    Jan 11, 2009
    Messages:
    5
    i usually get around 9-10 mph on my 225. t98-d18 w/od-4.88 gears. it runs a little rich but leaning it out makes it run poorly. rebuilt the motor about 10,000 miles ago. i was reading on the forum of guys getting 15-16! yikes
     
  9. Jan 15, 2009
    kaiser krawler

    kaiser krawler kaiser krawler 2019 Sponsor

    naples florida
    Joined:
    Apr 19, 2007
    Messages:
    113
    i'm getting 16-18 mpg, im' running a 420-3.73 gears and a stock gm 225 cam. it's also flat as a pool table around here. if you can get ahold of a g.p.s , check your odometer to see if it's accurate.
     
  10. Jan 15, 2009
    80cj

    80cj Member

    Hawaii
    Joined:
    Sep 1, 2003
    Messages:
    549
    My old 64 CJ-6 with 5.38 gears and a Chevy 283 got around 14 mpg and that went up to around 16 with a Warn OD. Let it break in and it should improve. You'll notice better throttle response as the engine loosens up and the rings seat. Don't drive at a steady speed and load the rings by accelerating up a moderate grade in hi gear. That will really seat the rings.
     
  11. Jan 15, 2009
    jzeber

    jzeber Well-Known Member 2019 Sponsor

    Morgan Hill, Ca
    Joined:
    Nov 15, 2003
    Messages:
    2,556
    Best I have gotten with my 231 is 18 mpg on a road trip to wheel near Tahoe. 4:88's, SM465 and an OD
     
  12. Jan 16, 2009
    juffer

    juffer Juffer 2020 Sponsor 2019 Sponsor

    Netherlands
    Joined:
    Jun 16, 2007
    Messages:
    210
    color of the sparkplugs? When light brown and, preignition 8 degress. You have the best you can get with the carb you have. Try the CO emission?
     
  13. Jan 16, 2009
    twiggs

    twiggs Work in progress

    Blue Ridge, GA
    Joined:
    Jan 26, 2005
    Messages:
    105
    In my experience, you'll see your best gas mileage when you use limited throttle and maintaine a steady speed........which is not what you should be doing really when you are breaking in an engine. Break it in properly and then check again.
     
  14. Jan 17, 2009
    John Worman

    John Worman from New Mexico

    La Luz, New Mexico
    Joined:
    Sep 22, 2002
    Messages:
    118
    When I bought my CJ5 with V6 in 66, I was dismayed at the gas mileage. I expected better after talking to others with that engine and rear ratio. It was about what your are getting and about what my 64 F head had been getting. After a few hundred miles and some new jets in the carburetor for higher altitude, things got much better. I got 18-20 mpg if I kept on the highway. If I went boondocking it dropped down, but it was still pretty good.

    I think you'll see a great improvement when the engine is broken in.

    John
     

Share This Page

New Posts