3.6 Trash MPG

[Str8uP]

What device or who re-calibrated your new tires? Did your gas mileage change when you went to 37's?

I get around 15mpg on 38's, 4:88 gears, using a Tazer JL Mini, daily driver and fully armored.

Our group found the 5:88 are a nice strong gearing, for gas powered V-6's. The pinion is more stout... until you move up to high performance axles. The bigger you go the more stuff breaks.

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[zrickety]

Hey guys - it's been a while but I am finally back in a JLUR and I'm having some issues with absolute trash fuel economy. My daily driving is 30mph or less for maybe a combined 3 miles so I'm not expecting anything great. Currently sitting around 13mpg (was around 10 with leaving it running during the winter). Did a roadtrip to my house up in Maine a few weeks ago, and the Lie-o-meter was 14.6 on the way (but there was a 30mph cross/headwind) and on the way home I squeaked out 15.6mpg. On the trip up, I went through 3/4 of a full tank of 87. Cruise control was set at 70 (which is actually 73) the whole time on the interstate, and up north was 10min trips at 35-55. Transmission had no problems hitting 8th and really never had to drop below 7th except for the occasional monster hill. The only thing to mention (mods below) is I have not adjusted my speedo for the tire height (but I've done the math).

2020 JLUR Hard Top
44k miles
3.6 Pentastar w/8spd
35" Duratracs @ 37PSI
PSC Bruiser Stubby with Warn Zeon 8-S
Factory rear steel bumper
No lift. No engine mods.

If your math is correct, you're getting about 16 mpg on the highway with heavy 35's on a heavy 4 door.
I'm on stock 33's in a 2 door (manual trans), I average 17 around town and the best I've seen on the highway is 23 going about 55mph.
If you don't have a check engine light, there is nothing to do. Put it back to stock and you might get a couple more mpg but there is no mystery here.

 

[Maverick909]

Does it really matter? This is the first JL I've had that I actually modded, but on other cars it hasn't made a difference as long as I know my actual speed (which I do).

Yes, programming matters. On the hwy with no wind resistance and avg slight hills. On 37’s and 4.88. Gears at 70 I can manage into the 18+ mpg drove out interstate 10 last weekend to elope in Joshua tree National park. The trip out ended up with 17mpg including a couple rather steep climbs with the rpm’s up at 3k for climbing for about 5 miles in total at the end. Coming home was a straight on head wind that killed mph down into the 10’s running 70mph. I also have the third pedal and two less gears. When I was running 35’s with 4.10 gears i avg about 16mpg if I was lucky.

 

[Maverick909]

What device or who re-calibrated your new tires? Did your gas mileage change when you went to 37's?

I get around 15mpg on 38's, 5:88 gears, using a Tazer JL Mini, daily driver and fully armored.

Our group found the 5:88 are a nice strong gearing, for gas powered V-6's. The pinion is more stout... until you move up to high performance axles. The bigger you go the more stuff breaks.

Do you mean 4.88 gears. Typically people on 38-40’s run 4.88-5.13 gears in that range

 

[Beachcomber72]

Does it really matter? This is the first JL I've had that I actually modded, but on other cars it hasn't made a difference as long as I know my actual speed (which I do).

You definitely need to program the vehicle for the 35’s to get best fuel economy. And your way over inflated on those duratracs.

1. Calibration of speedo
2. Adjust tire pressures to 32 psi.

As mentioned report back afterwards.

 

[Str8uP]

Do you mean 4.88 gears. Typically people on 38-40’s run 4.88-5.13 gears in that range

Good catch, proof read silly: 4:88 gears

 

[Maverick909]

Good catch, proof read silly: 4:88 gears

Lol I figured it was 4.88 great gear set and it is the stronger off the higher heat ratios for the D44

 

[jos]

Here what seems to be the cause....

https://www.carcomplaints.com/Jeep/Wrangler/2020/tsbs/tsb-0901222.shtml

 

[Deleted User 38384]

Shoulda Bought An EcoDiesel!!

 

[TxJeepers]

Been driving 3.6l Wranglers since 2012. It doesn't get good gas mileage. Maybe try 4xe or not a Wrangler.

 

[cainblue49]

Granted I am in Florida, however I think some of you have poor driving habits. 18 JLU, 35" not re-geared, with 2" lift. I average 20+ MPG mixed driving. Interstate over 65/70 sucks and drops to around 18. 70+mph, only when I can draft a semi. Tips - no need to be the fastest from the red light, it is a Jeep and you will see them all at the next red light anyways. When the light is red, let off, get out of the skinny pedal slow to a crawl rather than stop. Realistically, on a 15 mile drive with a couple red lights or stop signs mixed in, driving 10mph over the speed limit will not net you more than a minute or two of time on a thirty minute drive yet cost you $$ at the pump. Driving like grandma I can hit over 22.5 but extremly rare. Stuck in the city, 17-18 mpg. I time red lights, I do speed when it can keep me from stopping. My daily commute is 50-60 miles, mixed but primarily back/open roads for about 30 miles of it, driving between 60 and 65mph.

 

[BrentMG]

The best MPG I ever got out of my 3.6 JT Sport S was 17.6. Coincidentally, it was when I was driving it in to get traded in. The last time I filled up when I was about 2 hours away from Granger it shot down just over 2 MPG. It was crazy windy on that last leg.

Granted, I had 35s on it with the original gears, so that wasn't helping. Compared to my new JLUR with the 2.0L and 4.56s it is a dog. This new JLUR will run circles around my old JT. My new one is averaging just under 15 but it is getting better. That wind killed it on the way back home too. I had to deal with it from Iowa and Missouri.

 

[entropy]

MPG on a modified Jeep with the 3.6 is absolute trash. It is part of owning a Jeep. That's why they sell them all ugly with street tires, funny looking plastic bumpers, etc...13MPG is too low though.

Maybe it is because the 3.6 is a little sluggish at lows RPMs and needs to burn more gas to get moving? idk. My city MPG is trash, highway is ok.

 

[thekevin]

I have a 21 JLUR, 2.5" lift, 35" KO2's @ 35psi, bumper and winch on front, tire size recalculated with jscan. I can get 20mpg just running around the country roads at 55 - 60mph. When I get out on the highway it drops quite a bit the faster I go. 80mph it's down around 13mpg. That dip down at the bottom of the screenshot for several fuel ups was a trip from Missouri to Orlando pulling a small trailer with my kayak on it.


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[CarbonSteel]

MPG on a modified Jeep with the 3.6 is absolute trash. It is part of owning a Jeep. That's why they sell them all ugly with street tires, funny looking plastic bumpers, etc...13MPG is too low though.

Maybe it is because the 3.6 is a little sluggish at lows RPMs and needs to burn more gas to get moving? idk. My city MPG is trash, highway is ok.

Agree and think the gearing is the largest part of it (the 3.6L does not like to be "lugged") as well as speed. The MPG will exponentially drop as you go faster.

With 37" tires and 5.13 gearing on relatively flat ground and no head wind, if I drive ≤65MPG I can manage 19-20.

70-75 will be 17-18 and above 75 is <16. In town is typically <16 as well.

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