I thought I was being conservative. Upgraded my Rubicon JK 3.8 2011 dog last month. Rubi-Express 3-1/2 lift, and 285-70-R17 Goodyear Kevlars, right? Changed out the wheels also.
Now my mileage has plummeted from around 18 down to barely 14MPG. On the highway it is running at over 5000rpm much of the time just to keep itself at 70. (Auto, did I mention?) This is totally unacceptable. I went back to the shop and they have suggested: Cold Air Kit, Throttle Body Spacer, and re-gearing as possible solutions to get things back to decent mileage land. I hear the cold air kits/spacers are a waste of money. That leaves re-gearing unless someone has another solution.
Right now it has 411 gears from the factory. They suggest around 513...since I really don't understand this gearing world, someone reading this must and can advise me before I waste another pile of money. They also say I should not exceed 50 mph for the first 500 after re-gearing!! How do I get it home (3 hours of freeway awaits)?
Right now, I wish I had kept it stock.

 

70mph, 5000rpms? Ouch.

You'll want to check out some gearing charts but I think the 5.13 is probably a bit too steep of a gear for 33's. The 4.10's should be great. Skip the spacer, the cold air is more of a high flow filter (since it's not getting any cold air), and re-gearing......well that's $$$$ so you'll want to consider where you are and where you're going.

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Open the FAQ's (and any of the thousand other regearing threads on this site) for more info.

When you went to taller tires, did you recalibrate the speedo? Since the new tires are only minimally taller than the stock tires, that shouldn't be an issue, but...

The RPM charts in the faq's are fairly accurate, be sure to use actual measured tire height, not mfg spec.

5.13's are a good choice. Many like 4.88s, especially if you stay with 33's and don't intend to move up to 35's or bigger. And since you have a rubi, 5.38's are even an option worth considering, depending on future upgrade plans.

Seriously? You don't know how to drive under 50 mph? lol
How about spending an hour or two in/around town, driving to heat them up then stopping for a burger or something to let them cool, then repeat, before jumping on the freeway and sitting in the slow lane to head home? (many people don't even worry about breaking them in and are totally fine. But if you have an issue with them after install, you will probably want to be able to tell the installer how you broke them in to help with diagnosis)


This is dropping out of OD (probably down into 2nd?) going up steeper hills on the freeway, correct? Again, the new tires shouldn't be more than what, a 1/2" taller, than the stock 32's, so was there really a huge difference in power/shifting?


I would guess that you lost more mpg from the 3.5" lift and the loss of the forward rake, than with the small jump in tire size.

Just looked up the mfg specs:
Stock tire : 32.1"
New tire : 33.0"


That's why you do some research on sites like this instead of just handing over the credit card...

 

Mileage may be off if you're uncalibrated to match the tires and gears. If you have a GPS, compare the MPH at 10 MPH increments to get the offset ratio. I just drive with the GPS in calibration mode, on the highway, for my actual speed since mine is so far off...LOL

 

As suggested, check out the RPM charts. But, don't expect miracles from regearing. Also insure that you are not using the Jeep's computer to get your MPG miles--it's pretty inaccurate. Calibrate the speedometer (which also calibrates that MPG gauge and your odometers), then manually calculate gas mileage. If you didn't do that before, then you have no way to compare what you got before to what you're getting now--the MPG gauge just isn't reliable enough for that.

 

Your shift points may be way off. I have a 2011 jku with the 3.73 and 35"mtr and average 16.5 on the highway (75mph) and 14~16 around town, depending on how impatient I am. Get a procal or flashcal before spending any more money.

 

I'm getting about the 14.5-15.5 on 35s with 4.11s but I've got a 6 speed (same 3.8) and run a traildash. (Speedo is right on with my gps)

As others mentioned first check with a gps that your speedo is on. Secondly I'd try a procal or flashcal.

Also a lift will hurt your millage. The air running now under the jeep will mess up the aerodymanics. A few years ago someone posted millage results on a TJ that only had a 4.5 lift. It was still running stock tires and gearing.

FYI: You will never see stock millage again unless you stay stock.

 

Not sure about yours but mine runs 2500 rpm at 70 on a 13 3.6 rubi auto

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This is a perfect example why I'm so hesitant to do a lift and increase tire size.

 

I have a little over 3 inches if lift. My biggest mpg dropped when I got 15inch 10 inch wide steel wheels. Add brand new 33 inch tires to wheel. Its like driving with 4 boat anchors. I alway keep my rpms under 5000. I drive it at 3000rpms.