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Topic: Eco-jeep (Read 1688 times)

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  • jrainman13
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  • macgyver jr
Re: Eco-jeep
Reply #30
That's excellent especially with a lift kit. My xj might reach 18 highway with my lift on. Before it might reach 20. The most I ever saw was in my zj limited 5.2 4wd all time. Stock. City it ran somewhere close to 16 and I've seen highway as best as 24!!! I think that was before I put on the all terrains.

  • jrainman13
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  • macgyver jr
Re: Eco-jeep
Reply #31
Also. Just a thought. Would an mj fare better? I'm thinking this cuz of curb weight. An xj stock,  two door runs 2891pounds 4dr at 2993. The mj runs at 2912 swb and 2959 lwb. Both 4 cyl and 2wd. Now seeing as there is only a 12/pound difference on the low end fovoring the xj and a 34 pound difference fovoring the mj on the high end of things, does it/will it make that much of a difference in mpgs comparing the two? I've never driven an mj nor do I know much of mpgs they would get stock. I'm thinking power to weight ratios for the both of them are pretty spot on.

  • Rainman77
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  • Oilslick
Re: Eco-jeep
Reply #32

That's excellent especially with a lift kit. My xj might reach 18 highway with my lift on. Before it might reach 20. The most I ever saw was in my zj limited 5.2 4wd all time. Stock. City it ran somewhere close to 16 and I've seen highway as best as 24!!! I think that was before I put on the all terrains.

I did get up to 22 mpg highway on my full stock XJ. I get around 17 or 18 daily use
If it can't be fixed with a bigger hammer, it must be an electrical problem

Intsagram: jrain7 or jwrwoodworking

  • 1989comanche
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  • 1989 Comanche P/U
Re: Eco-jeep
Reply #33

Also. Just a thought. Would an mj fare better? I'm thinking this cuz of curb weight. An xj stock,  two door runs 2891pounds 4dr at 2993. The mj runs at 2912 swb and 2959 lwb. Both 4 cyl and 2wd. Now seeing as there is only a 12/pound difference on the low end fovoring the xj and a 34 pound difference fovoring the mj on the high end of things, does it/will it make that much of a difference in mpgs comparing the two? I've never driven an mj nor do I know much of mpgs they would get stock. 

My my mj was getting about 15 mpg with the 4.0, 5 speed and 3.07 gears on 31's. 


  • jrainman13
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  • macgyver jr
Re: Eco-jeep
Reply #34
So not really a difference. In fact it's worse. Then again that is some higher gearing. What about the 4cyl with say 3.93's? Or 4.11's? From the little I've seen the 4cyl jeeps came with lower gears to help with the smaller engine and whatnot.

  • G Beasley
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  • Sawzall Surgeon
Re: Eco-jeep
Reply #35
MJ might get worse mileage with the bed aerodynamics.


  • untchabl
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Re: Eco-jeep
Reply #37
My 99 XJ 2dr 2wd 4.0/aw4 with 3.55's gets about 21mpg mixed driving. Best so far has been 24.1mpg on a trip to Charlotte and back on highway 49. This kind of mpg has made me back-burner the 4x4 swap on it for awhile. That's on 235/75/15 highway tires, stock height, stock everything.
XJ Addict

99 XJ 2dr 2wd - SRT XJ coming soon
99 XJ 4dr 4x4 - Trail Beater
02 Suburban K2500 8.1 - Crawler Hauler

  • LBJ
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Re: Eco-jeep
Reply #38
that's really good.

  • jrainman13
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  • macgyver jr
Re: Eco-jeep
Reply #39
MJ might get worse mileage with the bed aerodynamics.

IIRC mythbusters did an episode on mpgs on f150's concerning bed aerodynamics w/tailgate up or down and other dynamics. The mini version test showed a swirling "vortex" of a sort in the bed and a second draft that essentially floats over the "vortex". It seems that the turbulence in the bed is bypassed. Does the truck bed create that much drag versus a cherocar?

  • G Beasley
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  • Admin
  • Sawzall Surgeon
Re: Eco-jeep
Reply #40
IIRC mythbusters did an episode on mpgs on f150's concerning bed aerodynamics w/tailgate up or down and other dynamics. The mini version test showed a swirling "vortex" of a sort in the bed and a second draft that essentially floats over the "vortex". It seems that the turbulence in the bed is bypassed. Does the truck bed create that much drag versus a cherocar?
It seems to have more drag , but its just a seat of the pants feeling .

  • cescuzzy
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  • Resident Electrical Wizard (Part-time)
Re: Eco-jeep
Reply #41
It seems to have more drag , but its just a seat of the pants feeling .

The pickup will have more drag, regardless.  It's not likely to affect the feel of driving so much as the mileage numbers. 

First, it takes time for that air pillow to form, and you get drag there.  Then the air flow over the pillow is not perfectly directed across the truck
  Some still hits the tailgate.  Lastly, any change in vehicle speed creates imbalance in the system, which creates drag.
A safety tip in the form of The Seventh Commandment of the Electrical Engineer: Work thou not on energized equipment for if thou doest so, thy friends will surely be buying beers for thy widow and consoling her in certain ways not generally acceptable to thee.

  • jrainman13
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  • macgyver jr
Re: Eco-jeep
Reply #42
Would a camper top then delete delete all that drag and make it just as much a brick as an xj? Even though it adds weight.

  • cescuzzy
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  • Resident Electrical Wizard (Part-time)
Re: Eco-jeep
Reply #43
Would a camper top then delete delete all that drag and make it just as much a brick as an xj? Even though it adds weight.

The drag would, at the very least, be as minimal as it could be, and the added weight would be negligible compared to the weight difference between the MJ and XJ.

Now, having said all that, without practical testing, there's no (simpler) way to know how much effect that drag even has on the mpg.  A lot of factors outside of the aerodynamics play into that.  Honestly, if I were to care about economy, I'd probably just get a hot hatch to drive.  I love my Jeep, but I miss taking corners too.
A safety tip in the form of The Seventh Commandment of the Electrical Engineer: Work thou not on energized equipment for if thou doest so, thy friends will surely be buying beers for thy widow and consoling her in certain ways not generally acceptable to thee.