Mod Effect on MPG

JrBiem

New member
I'll start by stating the obvious:
I didn't buy a JLU for gas mileage but...

Out of curiosity what kind of mileage are you guys/gals seeing lifted w/ bigger tires? I'm only averaging about 13.5 on the EVIC (admittedly need to hand calculate to see how accurate that is).

JLU Sport
3.6l
8 speed auto
3.45 gears
2.5" lift
315/70r17 nitto trail grapplers & 1 3/4" spidertrax spacers
tire size corrected with Tazer JL
dynomax muffler delete

Would re-gearing help mileage at all since the sport only has 3.45's?
 

Wranglerman

New member
As stated if your speedo is not calibrated for the larger tires what you are seeing for mpg’s is going to be incorrect but even with the speedo calibrated unless you do the regear yourself you won’t recoupe the investment in the long term, others may chime in and give their thoughts, I had a 2.5” boost done and am running 315’s on stock gears and yes I did see the mileage drop but that’s from the boost and larger tires, my JL does not seem to hunt for gears and I don’t see 8th gear on windy days but still getting between 19-20 on the highway and I can live with that
 

JrBiem

New member
As stated if your speedo is not calibrated for the larger tires what you are seeing for mpg’s is going to be incorrect but even with the speedo calibrated unless you do the regear yourself you won’t recoupe the investment in the long term, others may chime in and give their thoughts, I had a 2.5” boost done and am running 315’s on stock gears and yes I did see the mileage drop but that’s from the boost and larger tires, my JL does not seem to hunt for gears and I don’t see 8th gear on windy days but still getting between 19-20 on the highway and I can live with that

So what your saying is if the speedo isn't calibrated the EVIC is wrong and my hand calculated number should be better? And rgr on the re-gear thoughts. I don't seem to hunt for gears either, but never see 8th at all anymore.
 

JTCO

Meme King
Too many electronics on modern vehicles. If you don't change the obdii software to the current tire size that you're actually running, it can fuck up a lot of shit. Get a device to show the computer your actual tire size.
 

Too many electronics on modern vehicles. If you don't change the obdii software to the current tire size that you're actually running, it can fuck up a lot of shit. Get a device to show the computer your actual tire size.

I remember having to drive next to a cadillac with the big digital dash to find out how off my spedo was back in the late 90’s lol. Good times...
 

Wranglerman

New member
I used two apps to check my speed after my lift and tires and my speedo was off by 5 mph and if the speed is off the odometer is going to be off and the mpg’s will surly be incorrect as it’s based on the speed, once I plugged in my tire size to the Tazer the mpg’s returned to a more accurate number.

The two apps I used are Speedbox and Waze, Speedbox is just a speedometer and Waze even though it’s more a Navagation app it also has a built in speedometer, as far as the Tazer goes I tried measuring my tire size from crown to ground and it was still off so I kept bumping un the number on the Tazer and when I got to 34.49” it was spot on from 75 down is spot on.
 

JrBiem

New member
Getting close to 20 is when I drive, my average going back and forth to work in DT Houston has been running about 18 so a safe bet is I can get 17.5-19.5 city/hwy versus my 19-22 without the lift and tires

Thanks for the tips, I'll download the apps and double check the speedo then go from there. Just to be clear though, your showing those #s on rhe EVIC display, or they are hand calculated? Thanks again!
 

Wranglerman

New member
Thanks for the tips, I'll download the apps and double check the speedo then go from there. Just to be clear though, your showing those #s on rhe EVIC display, or they are hand calculated? Thanks again!


I am showing the average MPG on the EVIC display but this is after I corrected my tire size which in turn corrects the speedo, there are several ways to do this like thru the dealer if they know how or purchase a programmer and do it yourself, the hardest thing is getting those plugs out of the SGW module, I really should do a hand calculated mileage to compare
 

phljeeper

New member
Just use Waze and see what your speedo says compared to GPS measured speed. If you don’t have speedo correction then the Evic calculation will be wrong but so will your hand calculation as the mileage being tracked in the odometer is incorrect too as all of that ties back to the speed which needs adjustment for tire size change.


Sent from my iPhone using Tapatalk
 

JrBiem

New member
I am showing the average MPG on the EVIC display but this is after I corrected my tire size which in turn corrects the speedo, there are several ways to do this like thru the dealer if they know how or purchase a programmer and do it yourself, the hardest thing is getting those plugs out of the SGW module, I really should do a hand calculated mileage to compare

Just use Waze and see what your speedo says compared to GPS measured speed. If you don’t have speedo correction then the Evic calculation will be wrong but so will your hand calculation as the mileage being tracked in the odometer is incorrect too as all of that ties back to the speed which needs adjustment for tire size change.


Sent from my iPhone using Tapatalk

Alright, thanks guys. I do have the Tazer JL so I'll double check my speedo with the mentioned apps and change tire size if necessary.
 

Wranglerman

New member
Alright, thanks guys. I do have the Tazer JL so I'll double check my speedo with the mentioned apps and change tire size if necessary.

I believe the Tazer uses dynamic sizing for tire size so don’t use the info on the sidewall, I also found out when I did mine and measured from the crown to the ground as instructed that it was still off so I kept bumping up the tire size and checking with two GPS apps and finally landed on 34.49 for 315 KO2’s and my speedo is spot on from 75 down
 

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