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Discussion Starter · #1 ·
TJ Gas Mileage

I got my 98 sahara on the road about a month ago. I had not driven it all that much until today. The mileage sucks 12.5 on the highway, does this sound normal?
It has 31" tires & a 2"lift other wise its stock 4.0 auto trans.
Thanks Chris
 

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Re: TJ Gas Mileage

Is that actual mileage, allowing for the 10% difference in tire size? If not, it goes from 12.5 mpg to 13.75 mpg. That isn't terrible, but I get from 15.5-16.5 with mine with a 4.0 and 32's.
 

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Re: TJ Gas Mileage

Wow, 12-14 with a 360 and 35's doesn't sound so bad anymore. (and yes, my odometer is dead on correct.
 
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Discussion Starter · #5 ·
Re: TJ Gas Mileage

Upalittle are you also running an auto trans?
If so what rpm are you running @ 60 mph?
Mine seems high to me about 2900 rpm @ 60 mph
Thanks
 

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Re: TJ Gas Mileage

mine runs around 12-16 with 32's 3 inch lift and a few minor engine mods. But it is a 4 cyl.

I drive my diesle when I need decent mileage, 18 to 24 mpg in a full sized truck""
 
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Discussion Starter · #7 ·
Re: TJ Gas Mileage

Wow 12-16 with a 4 banger, maby 12-13 with a 6cyl isn't that bad after all.
Guess im just use to my daily driver S-10 gets 20 mpg with a 4.3l.
 

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Re: TJ Gas Mileage

You need to remember that a Jeep has the aerodynamic qualities of a barn. That sexy flat grill and windshield hit the air like a brick wall.
I've never checked my milage since;
A) I don't care.
B) I don't want to know how bad it really is.

With speed adjusted for larger tires, my 4.0/AX-15/3.73 runs about 2200 @ 60MPH. So your's does sound a little high to me.

So I guess my advice would be to stop worrying about your MPG and enjoy the Jeep for what it is.
 

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Re: TJ Gas Mileage

Actually my old DD 258 CJ5 with 33's is still getting 18 MPG. Just been checking last few weeks.

But you may not like to drive like I do or run my setup in order to get that type of milage. /ubbthreads/images/graemlins/laugh.gif

It's hard to compare one jeep setup is to another but there is a quick way and it will imediatly tell you if any change you make will help insead if waiting to go through a couple tanks of gas.

You need a stopwatch and a level road. (realy level not visually level.)

Maintaian a constant speed of 45 MPH and put the Jeep into neutral and time how long it takes you to slow down to 40 MPH.

This time repeat the test 25 mph and time how long it takes to slow down to 20 MPH.

The second part of this test will tell you what your rolling resistance is and can compair it to other jeeps. If you reduce your rolling resistance you will increase you MPG.

The first part has your rolling resistance and air resistance. Reducing your air resistace will help your MPG at high speeds. There realy is not much you can do here other than doing neat test with folding your windshield down.

If these two test match another jeep that is getting better gas milage then the problem is in the engine effinceny. Maybe a bad sensor if your FI or a carb running too rich. There can be a ton of stuff with a carb like vacuum leaks, bad power valves, high float settings... Wrong gap on the plugs can make the engine missfire and cost you gas.

f you want to get crazy you can weigh you jeep and find the frontal area and this will tell you the HP needed to maintain those speeds.

And you can pug those values into this equasion:
Image uploading. Refresh page to view


Good luck
 

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Re: TJ Gas Mileage

last i checked im getting right around 16 w/ 31" tires, 232,t-15,3.73

course thats by the odometer, so i figure she gives me 18ish
 

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Re: TJ Gas Mileage

No, mine is a 5 speed. I run about 2200 rpm at 65 mph. And I drive as easy as possibe trying to get all the mpg I can get. Only engine mod is a low restriction air intake.
 

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Re: TJ Gas Mileage

Yeah, that does sound a little low. My wife's 98 Sahara with 35s and a 5 speed (recalibrated speedo) gets 17 on the freeway and 14ish in town. My 04 Unlimited with 33s and a slushbox (recalibrated speedo as well) gets almost 17 on the freeway and 10-11 in town... however mine does have the overdrive tranny so maybe that's right... but also both our mileage goes in the tank over 70. Gotta love the aerodynamic qualities of a brick.
 

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Re: TJ Gas Mileage

That sounds a little low to me also. I get 15 city/18highway with a 4 liter, auto, 32" ATs and 3.73 gears. At 70 mph I am pulling 3k on the tach and my speedometer is right on. My only engine mod is a K&N filter in the stock airbox.
 

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Re: TJ Gas Mileage

[ QUOTE ]
Reducing your air resistace will help your MPG at high speeds. There realy is not much you can do here....

[/ QUOTE ]

Especially when you consider the SWB Jeep is about as aerodynamic as a brick house....
 

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Re: TJ Gas Mileage

My old slush box 4.0 tj got right around 10-14 mpg, i think 12-14 w/ a recalibrated speedo and unballanced 32" swampers. I was not a fan of the auto in a daily driver at all, no od, sucks a ton of power, just wan't fun.
 

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Re: TJ Gas Mileage

If you want to improve your fuel economy with a FI engine, move to the rocky mountains. Since there is less Air up there (less dense) the computer will pump less fuel in to the engine. Yes you will have less power, but mpg will go up.

For example. My Rubi has 33's. I recently drove to Colorado pulling and ATV on a trailer. In the flat lands of KS I managed 11mpg. In the moutains I managed to get 14mpg with the load. This is also the case when going to Colorado Snow skiing. Stock I managed 18mpg on the HW in KS (70mph) and in the Rockie I managed 20mpg.

Just some food for thought.
 
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