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post #1 of 31 Old 01-06-2014, 08:01 AM Thread Starter
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Why does my mileage suck?

I have a 2014 2 door sport 6 speed with 6k miles and 3.21's. It came from the factory with the steel 16's and tires that appeared to be borrowed from a Honda Civic. I have upgraded to some rubi takeoff 32's which made my speed read about 10% slow. I get about 230 (indicated) miles to a tank (+/- 17 gals) which should be around 253 actual miles. This comes out to about 14.9-15 mpg corrected. Is this right? I had an 89 yj with a 4.2 that got better mileage than this!

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post #2 of 31 Old 01-06-2014, 08:09 AM
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After i used the superchips flashpaq to recalibrate the speedo for bigger tires on mine it made a huge difference. I was getting roughly 13-14 mpg on 32.8" tires and now get 17-18 mpg depending on my driving habits. Worth the money IMO
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post #3 of 31 Old 01-06-2014, 08:23 AM Thread Starter
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Do you have a 3.8 or 3.6? Auto or 6 speed?

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post #4 of 31 Old 01-06-2014, 08:29 AM
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Quote:
Originally Posted by sixstring View Post
I have a 2014 2 door sport 6 speed with 6k miles and 3.21's.
^^^that's your issue, right there. The 3.21's are a killer when tire size is bumped up, even to just Rubi 32's. A regear would be the absolute #1 thing I'd put on my To-Do list.

And even with that, the JK is a bigger, heavier brick on wheels than the YJ was, so I wouldn't expect Prius-like mileage numbers anytime soon. I'd guess that the majority of people around here are going to be in the middle teen's for mileage. (I'm running 35's with 4.10's, drive 50+ miles daily on the highway, and get around 16ish mpg)

Your accessories will also make a difference. Are you running heavy full-width steel bumpers? Roof rack? Mexican midget luchador's hanging off of the spare tire? All of those will kill the mileage too.
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post #5 of 31 Old 01-06-2014, 08:37 AM Thread Starter
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I had a feeling I was going to need a re-gear sooner than later. I was going to save up for lockers since I need the larger carrier anyway. I can get some 4.10 gears with a stock e-locker for the back for free. Do you recommend the 4.10's if I have 35's in my future?

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post #6 of 31 Old 01-06-2014, 09:07 AM
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I have a 2014 Wrangler sport automatic and I get 15mpg. But I have some heavy stuff on it. 20" rims with 35" tires and full length steel bumpers with steel swing gate and spare, jerry cans, step bar and winch. All with the 3.21 you have also, I'm looking to regear in the future also.

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post #7 of 31 Old 01-06-2014, 09:54 AM
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Because its a Jeep.

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post #8 of 31 Old 01-06-2014, 10:01 AM
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Quote:
Originally Posted by sixstring View Post
I had a feeling I was going to need a re-gear sooner than later. I was going to save up for lockers since I need the larger carrier anyway. I can get some 4.10 gears with a stock e-locker for the back for free. Do you recommend the 4.10's if I have 35's in my future?
If you have a 6 speed the 4.10's should work great for 35's. I have a '14 auto with 35's and I have no plans to regear. I get around 14.5 mpg.


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post #9 of 31 Old 01-06-2014, 10:43 AM
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Quote:
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If you have a 6 speed the 4.10's should work great for 35's. I have a '14 auto with 35's and I have no plans to regear. I get around 14.5 mpg.
14.5? Holy Crap!! I have an 07 auto with 4:10's, heavy ass 35 Wildpeakes, Smitty bumpers/tire carrier, winch, a shit ton of lift and I get 16.8 pretty consistantly.

I'm running a Superchips on the 93 performance tune though.

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post #10 of 31 Old 01-06-2014, 10:46 AM
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Do you have a 3.8 or 3.6? Auto or 6 speed?
I have the 3.6 Auto
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post #11 of 31 Old 01-06-2014, 10:48 AM
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My 2008 w/ stock 4.10's and the 4spd automatic gets between 13-17mpg w/ my 315/75r16's (about a 34.5) depending on how and where I drive. I get my worst during the week, its cold so it warms up for about 10min in the driveway and I drive only in town to get to/from work. If I cruise down the interstate and keep my speed between 65-70mph it'll approach 17mg. During the weekends with a mix of city and highway driving it gets around 15-16mpg. On wheeling trips I typically manage around 15mpg. Less going up the mountain to get there and better coming back down.

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post #12 of 31 Old 01-06-2014, 10:50 AM
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With 3.21's and 32's your city will be terrible but your hwy should be incredible. Get a Aev Procal $159 is money well spent. Also how fast do you drive anything over 65 in a Jeep your going to lose big gas mileage due to its aerodynamics.

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post #13 of 31 Old 01-06-2014, 10:55 AM
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Getting that poor fuel economy, I would think it was do to the driver and poor driving habits.

I get 15 mpg with 40's on a 5000 pound 2 door with the 3.8, 6 speed, and 5.13 gears.

My wife gets 22 mpg on a stock JKU Sahara with 32" tires 3.8, 6 speed, 4.10 gears.

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post #14 of 31 Old 01-06-2014, 10:57 AM
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Quote:
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I had a feeling I was going to need a re-gear sooner than later. I was going to save up for lockers since I need the larger carrier anyway. I can get some 4.10 gears with a stock e-locker for the back for free. Do you recommend the 4.10's if I have 35's in my future?
I run the 3.8, auto, steel f/r bumpers, and 37s on 17" steelies and get 14.6-14.9 mpg without my spare on the carrier (when I drive conservatively - driving like it's rented it drops to mid-to-low 13s). I have 4.88s and in hindsight, wish I'd gone 5.13s. The 4.88s were perfect with 35s, but since moving to 37s, I have a hard time keeping in OD with every slight incline or headwind on the hwy.

From what others have said the 4.10s should work well with the 3.6 to 35s and bearable with 37s.

I do know that the e-locker won't work in your d44. The carrier/locker for the rubicon d44 is offset compared to the X, Sport, Sahara.

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post #15 of 31 Old 01-06-2014, 10:57 AM
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Quote:
Originally Posted by jdemonto View Post
With 3.21's and 32's your city will be terrible but your hwy should be incredible. Get a Aev Procal $159 is money well spent. Also how fast do you drive anything over 65 in a Jeep your going to lose big gas mileage due to its brick like aerodynamics.

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post #16 of 31 Old 01-06-2014, 11:09 AM
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I drove from Mesa AZ. 85209 up through the Flagstaff way (due to weather) over to Westford Ma. 01824. About 2750 miles. From my expense report, 212 gallons of gas, around $800. Close to 13 MPG. Brand new 38 MTR's, 5.38's, 3.8 auto, usually drove 75+. I don't pay for it. I gotta drive back in 3 weeks. I'll let ya know.

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post #17 of 31 Old 01-06-2014, 11:36 AM
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I have found that if I drive at 65-70 my mpg is best on the highway, I ran 35's with 3.12's for over a year and my mpg sucked, 4.88's now with a 6speed two door, 35's and a mpg tune I now get 16.5-over 18+. Wind does play a factor in it tho. I have no tire, or big ass bumpers.


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post #18 of 31 Old 01-07-2014, 06:49 AM Thread Starter
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I'm sure my driving habits aren't reflective of someone who is too concerned about mileage, but I do about 50/50 hwy city driving. Here in Texas the speed limits are usually 75 on highways, if you drive below 70 you will most likely be run off the road. I would think that the 3.21s would be great for 75 mph driving, my rpms never cross 2500, but I guess at that point wind resistance takes over.

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post #19 of 31 Old 01-07-2014, 07:05 AM
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Quote:
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I'm sure my driving habits aren't reflective of someone who is too concerned about mileage, but I do about 50/50 hwy city driving. Here in Texas the speed limits are usually 75 on highways, if you drive below 70 you will most likely be run off the road. I would think that the 3.21s would be great for 75 mph driving, my rpms never cross 2500, but I guess at that point wind resistance takes over.
3 inches of lift - 37's - VKS rear bumper <<-- BIG & BEEFY, especially when I have my spare on it - steel tube fenders... I've never had a problem getting run off the road or having people letting me in (even when they try not to) down here in SA. I'm usually running right at 60-65 mph. Going above 65 really REALLY burns up the gas

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post #20 of 31 Old 01-07-2014, 07:18 AM
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Yeah, rpm wise it should be great. Same thing with my 4.10's and 35's. Problem is aerodynamics and poor engine performance. My 3.8 can't keep it at 75 here in CO w/o downshifting all time. That's why I set the cruise for 65-70. At least then when it drops into 3rd gear the rpm's stay reasonable. It also doesn't have to downshift as much.

On the highway I basically just tuck in behind a semi and stay in the slow lane. It does get annoying sometimes being in as new and expensive a vehicle as the JK and having to slum it in the slow lane though. I could go faster but it's not worth pushing the jeep that hard either. Once I get the Hemi swapped in though I doubt I'll be able to stay out of the fast lane.

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post #21 of 31 Old 01-07-2014, 07:53 AM
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Quote:
Originally Posted by sixstring View Post
I had a feeling I was going to need a re-gear sooner than later. I was going to save up for lockers since I need the larger carrier anyway. I can get some 4.10 gears with a stock e-locker for the back for free. Do you recommend the 4.10's if I have 35's in my future?
Based on the gear chart, if you have plans for 35's, then 4.10's would definitely be a good choice.

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post #22 of 31 Old 01-07-2014, 08:15 AM
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Hmm my 2013 2 door Rubicon 6 speed gets 19-20 MPG average for me and I run my tires at only 27 psi front and 20 psi rear (mix of city and hwy). I suspect your 3.21s or your driving style is the killer. Even with 3.21s though the transmission ratios of the 6 speed are far more aggressive in the first 4 gears than the older 5 speeds were. How is your driving style? All stop and go driving or some hwy?
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post #23 of 31 Old 01-07-2014, 06:53 PM
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Wow. Some of you guys are lucky. My stock 2door rubi with 4.10's gets about 13.5 in town and at very best 18 on the highway. My 2007 rubi was about 3 mpg better in both. I'm def easy on it too.

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post #24 of 31 Old 01-08-2014, 04:53 AM
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14.5? Holy Crap!! I have an 07 auto with 4:10's, heavy ass 35 Wildpeakes, Smitty bumpers/tire carrier, winch, a shit ton of lift and I get 16.8 pretty consistantly.

I'm running a Superchips on the 93 performance tune though.
My '09 Rubi with 6sp, 4.10s, 33's only got 15mpg. Hell, the 2014's are rated at 17 city but have no idea what gearing that is for and it is probably driving like an old lady. I can get 15.5 if I drive ever so careful like Miss Daisy. I think that the 35" MTR's have a lot to do with it. Heavy and a lot of grip on the road --- A LOT of rolling resistance.


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post #25 of 31 Old 01-09-2014, 07:52 AM
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These gas mileage threads suck because there are so many of them. But I wanted to chime in here because no one has addressed the fact that the OP isn't correctly figuring out what MPG he is actually getting.

Unless they made the tanks bigger on the new 2 doors, I don't think he's getting 17 gallons in the tank. The tanks have a pretty big reserve capacity. Divide the mileage you get on a full tank by the amount of gas it takes to fill it back up. If you're only getting 14 or so gallons in there on 230 miles then you would be at around 16.5 which is definitely plausible in real world driving, especially in winter time.

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