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Old 09-19-2019, 08:28 AM
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Improve Gas Efficiency

I know this was a thread somewhere else some time ago but couldn't find it anywhere. In that thread it spoke of an electronic device when installed made for better gas efficiency when running larger tires than stock. I am now on 34's with 1.5" spacer. I have a 75th Anniversary so had a hard time dealing with losing the stock wheels. Nonetheless... anyone remember this thread? There was some great advice on there.

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Old 09-19-2019, 08:51 AM   #2
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I've never seen anything that improves gas mileage, all have been snake oil.

If you've changed your tire size you need to tell the computer what you've done to correct the speedo. Also any MPG the Jeep computes will be inaccurate until this is done. There are several options; Superchips, AEV, Bully dog all have programmers. Some of them even offer "tunes", but again IMO they're snake oil.
The newest kid on the block is Jscan for updating gear, tire size, etc. I switched our 2018 JK from superchips to Jscan just to check it out. So far I really like it, an it's super affordable.

Good luck!

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Old 09-19-2019, 08:51 AM   #3

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A device like an AEV procal or similar device will correct your speedometer and shift points on an automatic (speed is one of the things that control shift points so if speedometer is off so are shift points) it might help mpg by shifting at the proper times and keeping your foot off the gas. It also corrects odometer so you will see actual mpg.
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Old 09-19-2019, 12:40 PM   #4
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I spent time measuring miles traveled vs. tire height setting in the computer, resetting with the Superchips flashcal. I found the factory setting to be .5" too high for the stock KM tires, and .75" high for Falken AT3W in 235-80-17. Thus it seems that the factory was cheating me out of a few miles of warranty while giving a falsely inflated mpg reading on the instrument panel evic.
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Old 09-29-2019, 02:50 PM   #5
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I got a 1 mpg increase by removing the helmholtz resonators.

I lost the increase by installing the leveling kit and geometry bracket. The forward rake that is stock does improve air flow over the vehicle.

Like jadmt wrote, if you increased the tire size, you need to recalibrate your transmission for the higher tire size. That should be your first thing you do. I use (and recommend) the AEV Procal as well.

Best of luck!
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