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Unread 03-05-2014, 07:22 AM   #1
tramark100
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2011 JK Unlimited-Poor Gas Mileage

I have a 3.8 automatic 4dr, rag top, low restriction intake filter, performance exhaust. The vehicle has a 3" lift, running 35's.

Has anyone tried any of the performance chips or programing products to increase mileage and performance on a 3.8 V6? Only getting 14 to 15 miles per gallon average.

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Unread 03-05-2014, 07:29 AM   #2
JBTJ
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For your MPG's, did you recalibrate the speedometer after you installed the 35's? If not, that's your problem.

As for performance, did you regear to accommodate for the 35's tires? If not, that's your problem there too.

None of those performance chips or programing products will do you one bit of good. Except make your wallet lighter.
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Unread 03-05-2014, 07:41 AM   #3
wilywillie
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I get 15mpg in my '08, after it's been adjusted for 32" tires, and running 3.21 gears.... 2" lift, steel bumpers, winch, gear, etc. (lots of extra weight)


With an automatic, like LB said, using a computer flash will help with both your tire size and your "shifting", and if it's not calibrated already, you'll see a HUGE jump in perceived mileage. 15mpg in a 4dr with 35's is pretty darn good, though....be happy Atlanta's pretty flat:-)
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Unread 03-05-2014, 07:53 AM   #4
Jared89
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yeah i really dont know what the op is complaining about 15mpg isnt bad.
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Unread 03-05-2014, 07:56 AM   #5
cobra671
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Quote:
Originally Posted by Jared89 View Post
yeah i really dont know what the op is complaining about 15mpg isnt bad.
Lol!! That's what I get on my stock 2011 2 door rubi with a hard top and 32" tires. So I think he's doing pretty good with his tires.
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Unread 03-05-2014, 08:08 AM   #6
duneslider
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If you aren't recalibrated for the tire size and if you haven't regeared that is where you should start.

i have a 3 inch lift and 35's and regeared to 5.13 and I typically get between 15-16.5. Over the last year my calculated average is 15.5. I drive pretty conservatively but cruise at 75 on the highway daily.

So, you really aren't too far off. I didn't see a huge jump in mileage regearing but it is much nicer to drive and my transmission temps stay lower.

The intake and exhaust probably provide no benefit to efficiency in these computer controlled jeeps.
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Unread 03-05-2014, 08:37 AM   #7
JIMBOX
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Heh Heh the old standby-My '08 JKUR/regeared/33.6" tires/weight avg 5600lbs-avg 17.2 mpg at 70 mph-

Dual cat-back exhaust/aux coolers/light foot-

The never ending story

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Unread 03-05-2014, 11:39 AM   #8
planman
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Regear to 5.13s or 5.38s to improve fuel economy on a '11 automatic with 35s.

Transmission downshifting/gear hunting is what kills fuel economy.

Regear to produce high enough engine rpm to produce enough power to reduce frequent downshifting, and fuel economy goes up.
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Unread 03-05-2014, 02:17 PM   #9
tramark100
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Approx price to switch to 5.13 gears
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Unread 03-05-2014, 03:11 PM   #10
JBTJ
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Quote:
Originally Posted by tramark100 View Post
Approx price to switch to 5.13 gears
Area dependant, $1000~$1200 for both axles.
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Unread 03-05-2014, 03:18 PM   #11
planman
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Quote:
Originally Posted by tramark100
Approx price to switch to 5.13 gears
Like he said, the labor cost is area dependent.

You can get gears and overhaul/bearings install kits for less than $600.

It is rated at a 10 hour job. Experienced installers do it in less time.
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Unread 03-05-2014, 03:39 PM   #12
JIMBOX
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It'll depend on the State/County/shop/sales and what other diff work you might/should have done at the same time-


Quote:
Originally Posted by tramark100 View Post
Approx price to switch to 5.13 gears
Price range from $1200 bucks to $2500 bucks and all ranges in between-

The type/quality/completeness of the regear--ie: full rebuild kits or ???

Do a lotta homework before making the decision, cause you don't getta money back guarantee for the wrong decision-

Good luck

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