spots vs rubicon mpgs - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 16 Old 08-16-2014, 01:15 PM Thread Starter
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spots vs rubicon mpgs

Ok I had a 2014 jku sport with auto and 3.73s at the first oil Chang the dealership forgot to put the oil filter cap on and cooked the motor. After some real bitching I traded it for a new rubicon jku it also has a auto and 3.73s. My question is with the sport I was getting around 18-19 average 20.3 mpgs on a real good day with the rubicon im only averaging 15.5-16 mpgs. Is it the tires making the diff in mpgs? both are 100% stock
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post #2 of 16 Old 08-16-2014, 01:29 PM
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Unless Jeep has made a change the Rubicon comes with 4.10 gears that plus the larger tires would make for your difference. Another factor that you didn't specify is whether you are using the computer for results or are you doing real world fill and mileage calculations.

Last edited by 4x4x4; 08-16-2014 at 01:31 PM.
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post #3 of 16 Old 08-16-2014, 01:37 PM
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'14 Rubis come with 3.73s, 4.10s are optional now. As for mileage, I have the Rubi X with 4.10s and average 17.6 mpg.
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post #4 of 16 Old 08-16-2014, 02:21 PM Thread Starter
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Ok its only on its 3rd tank hopefully it will pick up some as it gets broke in
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post #5 of 16 Old 08-16-2014, 02:23 PM
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Yeah, you have to opt to have the 4.10's in the Rubicon's now.

Those tires would make a fairly noticeable impact on MPG's. Also, your Jeep is heavier now. Was every other variable the same? Power windows, locks, hardtop, softtop, etc? If so, the JKUR adds probably a couple hundred pounds on a Sport. That combined with the tires and the fact that Rubicon's tend to sit a tad higher than a Sport, would be enough to drop the MPG's a little.

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post #6 of 16 Old 08-16-2014, 02:48 PM Thread Starter
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Yes they have the same options
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post #7 of 16 Old 08-16-2014, 03:00 PM
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That break in period will matter too. I believe it takes like 1k miles? I'm not sure...

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post #8 of 16 Old 08-16-2014, 03:48 PM Thread Starter
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I currently have just over 600 miles on the rubicon. I thought it was just a tad low when I have read about others with 35s getting better mpgs than I am in stock trim. Would a cat back system and cold air intake do anything to help with mpgs or power? I have read many different post about this with no definitive answer I know its not going to be a power house but anything helps
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post #9 of 16 Old 08-16-2014, 07:45 PM
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Do you have auto or manual?

I thought the 4.10 gears were still standard on the manual.

At least, it shows 4.10 axle ratio as an automatically checked box with a cost of zero when you have manual selected as the transmission on the "build and price" site, but the price changes to $495 when you select auto.

It's weird because when you look at the spec comparison page it shows 4.10 as "Available" on the Rubicon, not as standard. Yet it shows the other two ratios as "Not Available" on the rubicon. Odd.
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post #10 of 16 Old 08-16-2014, 08:29 PM Thread Starter
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It is a automatic. On the window sticker there is no charge for the 4.10s. I'll contact my dealer and get a build sheet on my jeep to dubble check the ratio
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post #11 of 16 Old 08-16-2014, 08:32 PM
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If 4.10's aren't on the right side of the sticker with an up charge, it has 3.73's.

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post #12 of 16 Old 08-17-2014, 06:32 AM
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I just had a couple friends who bought 2014 rubicons recently and I was talking to the dealer about this very same gear ratio issue. It turns out that the 4.10's are standard in the manual but an option in the automatic. If you have an automatic and the window sticker doesn't show an up charge for 4.10's on the right side of the sticker, then it has 3.73's.

Seems a little backwards to me...


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post #13 of 16 Old 08-17-2014, 06:57 AM
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I haven't checked the mileage by hand yet because I figure it is what it is.

The MPG meter built in usually says between 17-21, depending on how much highway/city/rural driving I've been doing. Around town it usually shows 17-18 depending on traffic, lights. etc. On rural roads (55 MPH, not too many stops) it shows 20-21. On the highway (65-70 MPH) it shows around 17-18. This is a two door Rubicon, mostly stock.

I may eventually start calculating it myself when I fill up, but so far I haven't bothered.
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post #14 of 16 Old 08-17-2014, 07:05 AM
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Quote:
Originally Posted by NGINIER View Post

Seems a little backwards to me...


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I wonder what the actual transmission ratios are between the manual and automatic. In many vehicles the manual has a higher numerical final drive ratio than the automatic because the torque converter has a torque multiplication effect, as well as giving a higher RPM due to slippage when the converter isn't locked. If the transmissions are similar, they get the final drive difference by having different axle ratios.

If the transmission gear ratios are somewhat similar between the current 6 speed manual and the automatic, it wouldn't be surprising that they put slightly higher gearing (lower numerical ratio) in the axles.
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post #15 of 16 Old 08-17-2014, 09:04 PM
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Oh, and for comparison, I have a 2dr, manual rubi, stock.....less weight than yours, no loss due to the slush box, and I still get only 18mpg on the highway or in town....I would guess the additional tire weight and resistance over the sport is your difference.....16 mpg in an auto 4dr sounds about right....it's a heavy wind brick with knobby tires....

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post #16 of 16 Old 08-19-2014, 02:38 PM Thread Starter
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Thanks for the info. I got with my local dealer and I do have 3.73s (when did they stop with the axle tags anyway?). So in just going with it the differance in tires causing the lower mpgs.
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