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Discussion Starter #1
How many miles does everyone get roughly in their JK? Few months back, I had 31 inch tires and I traveled cross country to Colorado and I got roughy 150-250 miles on a tank of gas. I thought nothing of it until I saw someone else post about bad gas mileage in their jk and it got me thinking. I just put 35s on last week, filled up yesterday, and drove maybe 30-40 miles between now and then, and I'm already at 3/4 of a tank. Anyone else have any problems? Is this normal? Any suggestions to get this fixed? Thanks in advance.
 

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My last tank with stock rubi tires was 15.3 mpg. I get about 240 miles on a good day before the red light comes on. Usually around 220.

I have never seen 17 city, 21 freeway.
 

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i have a JKU 13 and i get 18-21 mpg on the freeway
on the city i get around 16-18
I changed tires to size 31 and wheels 17 and it made no difference in mpg's
however when you change tire size you have to tell your computer you changed to a different size tires, it is thinking it still has the stock size tires.

Back to the gas mileage.. that is a pretty bad mileage!! i do see a big difference on mpg if there is wind, but never that bad. Another thing that it might be your case..
Do you know whats your gear ratio?
I have 3.73 you might have a lower gear ratio and that can affect your mileage big time, specially if you went to a 35 size tires.
What year is your JK?
 

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I have had two 2015 wranglers, one sport and one hard rock. Both with 3:73 gears. The sport averaged 18.1 MPG all around and I do about 500 miles a week. The hard rock averages about 16.5 taking the same route. I believe the tires are the reason for the difference.
 

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Discussion Starter #5
It's a 2011 and the gears are the stock 3.73s, I was expecting a big hit with the 35s, I just didn't know if the 31s should be as bad as they were on mileage
 

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When I went to 35s from stock Rubis (30.75 diameter) I didn't really notice to bad of a hit in mpgs( 3.73s). I could tell they were heavier from a go but still averaged around 15 city just like the rubis.
 

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2015 JKU Hard Rock and I'm getting 15.7 all around average. Mixed commute, wheeling, and some trips that are all highway. We just did a weekend in VT, 870 miles round trip almost all highway, got 17.9 on that one. Stock 32" Rubi tires and I lifted it 2,800 miles ago, which had no impact on mileage. 4.10 gears.
 

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I get 42mpg on 37's @ 80mph uphill...sure I do!

13 to 18 depending on Wind, uphill or downhill and speed

14 is average all around
 

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The one thing that everyone must realize is that tire size will have a huge impact on economy. Sometimes people will put on bigger tires without re-gearing or re-programming the computer, and then are shocked when their mileage goes down the toilet. Take a kid at work as an example: he bought a '12 sport with 3.21 gears, then lifted in a couple inches and added 35" tires! He was really disappointed when he couldn't use 6th gear anymore because of the bigger tires, but was REALLY shocked when his mileage dropped by about half! I talked him into a regear to 4.11's, which really helped his lack of power, then had him get a programmer to tell his computer that he had different gears and bigger tires. He was simply amazed when things got closer to normal! His economy was not quite as good as before, but at least he got back into the double digits!
 

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Going to larger tires not only affects your speedometer which everyone talks about, but your odometer as well. If you go from 245/70R17 (30.5") tires to 285/70R17 (32.7") tires, your speedometer will be 7 percent fast. The speedometer calibration which registered 70 now correctly will still read 70 only you will be traveling at 75. Driving 300 miles will now suddenly only register 280 miles, not too terribly off. But when you calculate your mileage, you burn the same gallons, but now your miles are fewer so your MPG appears to be lower.

Bump the tire size up to 315/70R17 (34.4") and when the speedometer says 70 you will actually be traveling at 79. Those two check points that were 300 miles apart suddenly will appear to have shrunk to 265 miles apart. And you fuel mileage just got 12% worse, instead of 18 your calculation gets you 15.9 MPG.

Recalibrate and your speedometer says your going 70 when the GPS says your going 70, the two points 300 miles apart are 300 miles apart again and now your mileage is back up to 18. Recalibration does not actually change fuel mileage, it just corrects the factors for it's calculation.

Note - the changes in MPGs do not take into account the increased drag of heavier tires and wider tires, both of which are detrimental to fuel consumption.
 

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Discussion Starter #12
I understand that lifting and getting bigger tires throws everything off, you can read that in almost every thread. My main question was how many miles does everyone get on a full tank of gas. 200ish miles on an 18 gallon tank just didn't seem right to me when I was on 31s.
 

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That is low. I track my mileage, have for over 30 years. It tells you a lot about the state of your vehicle, which can vary depending on condition or if you are towing something for example. My Sahara came stock with P255/70R18 Bridgestone Duelers and has the 3.21 gearing. The furthest I have driven on a single "full" tank is 353 miles which was all highway miles. The MPG on that tank was 21 the previous two tanks, also mostly highway miles were 21 and 20 respectively. The worst tank so far was 16 and that was mostly stop and go heavy traffic (a rarity for me). I usually fill up at about 1/4 tank or around the end of the month (which ever comes first).

Lando76 - the stock tires on a Rubicon (at least the 2015s) is LT255/75R17 which is a 32" tire. The TJ Rubicons had a 30.5" tire, and that may have carried over to the early JKs, I am not sure.
 

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Discussion Starter #14
When I went on my trip, I was driving through Kansas which was mostly flat, and has stations were a rare sight, I stopped to fill up every 150 miles or when I got to 1/4 of a tank, which ever came first. Like I said before I expect terrible gas mileage, I just didn't expect to only get 200 or so miles out of a full tank of gas.
 
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