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Unread 11-10-2010, 09:25 AM   #1
buddastrat
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Mileage of early TJ's vs. latter

Why did the early ones get decent mileage? I was getting 20 mpg with city/HW driving in a '97. My '98 was real good too. About 17, but I put on 31's. Speedos was calibrated.

My 06 is miserable. Doesn't help that it's a rubi and I read it carries an extra 500 lbs. But still way low. Even with a six speed that lets me keep RPM's a bit lower with city driving.

On this site, it reports earlier TJ's did get better mileage. Are there more emission stuff on the later ones?
http://www.fueleconomy.gov/feg/bymake/Jeep1997.shtml

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Unread 11-10-2010, 10:03 AM   #2
fang_x
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the newer ones in theory should have better gas mileage because of the rounded mirrors, they are more aerodynamic then the square mirrors of prevouis years.
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Unread 11-10-2010, 10:15 AM   #3
BYuen
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The later model TJs do have more emission controls than earlier models, but I'm not sure how greatly it affects mpg.
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Unread 11-10-2010, 10:20 AM   #4
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Quote:
Originally Posted by buddastrat View Post
Why did the early ones get decent mileage? I was getting 20 mpg with city/HW driving in a '97. My '98 was real good too. About 17, but I put on 31's. Speedos was calibrated.
I got 18+ mpg highway with my 98' 5 speed with 35's and stock 3.73 gears.My brother's 05' 6 speed Willy's edition on 35's with stock gears gets the same.
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Unread 11-10-2010, 10:48 AM   #5
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Originally Posted by BYuen View Post
The later model TJs do have more emission controls than earlier models, but I'm not sure how greatly it affects mpg.
I think you're probably right.

The later models have a redesigned intake manifold to make up for power losses caused by the controls on the exhaust. The redesigned intake manifold lets more air into the engine (and consequently burns more fuel) raising power back up to where it should be.

I'm guessing since the engine is burning more fuel to produce the same power, that's why your mpg sucks so bad in later years. Sorry guys. But thanks for not killing the planet!

It's a popular swap for older style Jeeps (TJs, XJs, and Grands)... I've read gains of anywhere from 10 to 25 hp.

Old style left, new style right:



My '98 (3.07's on 31's, never use 5th gear) gets 15-16 mpg on a 50/50 mix of city/highway, though I have a depleted uranium right foot.
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Unread 11-10-2010, 12:15 PM   #6
buddastrat
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Quote:
Originally Posted by TheBoogieman View Post
I got 18+ mpg highway with my 98' 5 speed with 35's and stock 3.73 gears.My brother's 05' 6 speed Willy's edition on 35's with stock gears gets the same.
All highway I was able to get in the 20's, with 31's. Look at the link I posted. It shows the mileage dropping every few years.
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Unread 11-10-2010, 12:22 PM   #7
buddastrat
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Quote:
Originally Posted by PDX_XJ View Post
I think you're probably right.

The later models have a redesigned intake manifold to make up for power losses caused by the controls on the exhaust. The redesigned intake manifold lets more air into the engine (and consequently burns more fuel) raising power back up to where it should be.

I'm guessing since the engine is burning more fuel to produce the same power, that's why your mpg sucks so bad in later years. Sorry guys. But thanks for not killing the planet!

.
Is that why the HP increased? I think around '01 it went up. The latter ones did seem a little more peppy to me. Back in '06 I read some report on 0-60 times where the 05-06's had the best times, due to the revised engine and six speed. But it's such a guzzler.
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Unread 11-10-2010, 12:32 PM   #8
jeep308
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it tells about the increases and what was changed to make the power increase in the TJ specs in the FAQ
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Unread 11-10-2010, 01:42 PM   #9
ChuckPink
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I have an 05' with stock 3.73 gears and 31's and I have always gotten 15 MPG consistently........Drives me nuts. Plus almost 90% of my driving is highway miles.
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Unread 11-10-2010, 02:49 PM   #10
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The 6 speed manual isnt much better than the 5 speed as far as the overdrive goes. Just has a taller first gear
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Unread 11-10-2010, 03:48 PM   #11
j_niko
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My 2000 with 4.0l and 33s - 12 MpG
97 with 4.0l and 31s - 16 MpG

My 2010 Challenger R/T with a 5.7l hemi - 25.5 MpG

I still can't reason that one out......
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Unread 11-10-2010, 04:04 PM   #12
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Quote:
Originally Posted by j_niko View Post
My 2000 with 4.0l and 33s - 12 MpG
97 with 4.0l and 31s - 16 MpG

My 2010 Challenger R/T with a 5.7l hemi - 25.5 MpG

I still can't reason that one out......
Doesnt the 2010 have the engine that runs on 4cyl on the hwy? Also it doesnt have the aerodynamics of a barn
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Unread 11-10-2010, 04:55 PM   #13
chris142
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My 02 sure seems gutless compared to older TJ's and YJ's that my customers bring in. I bet their mpg is better than mine too.
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Unread 11-10-2010, 05:10 PM   #14
terpsmandan
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05 with 3.73 and a 6sp and I get between 16 and 18 mostly highway.
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Unread 11-10-2010, 05:16 PM   #15
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My 99 swb with a 4.0l and a 5 speed and 31's. I used to get 25 mpg no matter where I went city or hwy.

My 06 LJ rubi with an auto and 31 's. I can get 19 mpg. if I get on a flat stretch and use the cruise control. around town, it ranges all the way down to 10mpg.
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