3.6 Trash MPG

[TheRaven]

Mythbusters proved that the tailgate up/down theory had no measurable changes to MPG. I'm guessing the bed cover would be the same with/without.

Tonneau covers do improve fuel mileage. That's a well known fact (well, among truck guys that is). How much is where the dispute lies. I'll be adding one to my Silverado in the coming months so i'll be able to add some data to the argument.

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[chadk77]

I'm running BFG KM3s - 37x12.50s, with 4.88s and I'm averaging 16 mpg. Tazer corrected for tire size and gears and try not to drive like a bat out of hell. If I go super easy I can eak out 17 some days if there's zero wind. lol.

 

[jmj8355]

ill throw my 2 cents in and say i drove a 3.6 JLUR for 20k on stock 33s and around the best i would ever see was 16mpg with mixed highway and city although i have to disclose it was a 6 speed. What a horrible driving experience that was. I now have a JLUR with the 4 banger and never see below 20mpg on the same routes plus i have 35 K02's on. Great Engine and such a better daily drive although sounds like a blender.

 

[Dailydrivenwrangler]

2021 JLUR 3.6 etorque with 8 speed and stock gears. Stock height, stock bumpers 35” Duratracs and I’m in the 18-20 mpg range with my hardtop. 37” Patagonias and soft top and I’m in the 16-18mpg range. That’s hand calculated running 89 octane and putting on about 700 miles per week.
I have gotten up to 22-24mpg per tank but those times I had a heavy tail wind so they were not realistic. I let the tranny stay in whatever gear it wants. 6th, 7th or 8th I don’t care. I find if it’s holding 7th and I manually bump it up a gear that I will lose a tiny bit of milage so I let the computer decide where it’s happy.

My max speed however is only 60-62mph. If I bump it up to 65-70mph I will take 2mpg off each of those numbers.

 

[Vatdevil]

Cruising at 70 in a Jeep brick will tank your mileage much more than just about any vehicle.

 

[J.Ferreira]

Use the Fuelly App to track your mileage after you adjust the computer for the larger tires.

Seconded

 

[J.Ferreira]

@MEski4x4,

Ken, in no way am I experiencing your crappy mileage. My 2019 JL 3.6L 8-speed is lifted on 35's and I routinely get around 8mpg better results. I'm typically between 20 (worst) to 24 (best) driving around metro Denver. That's even with much less ambient air. We're a mile higher up in altitude here.

Even 4 wheeling in the mountains in CO I get better mileage in 4Lo than you are in 2Hi within MA.

Something is certainly wrong. Here are a few things however to compare and contrast.

- 2 door vs 4 door
- Sport vs Rubicon
- I use a Tazer to set my Tire Diameter. But then disconnect it. I use none of it's 'Live' features.
- I do leave my ESS enabled.
- I run nothing less than 91 octane. To prevent or greatly minimize knock potential at altitude.
- My on-road tire pressure is typically around 40 to 41 psi (temperature dependent). I do lower down to low 30's in deep snow and 15psi off-road everywhere.
- I'm pretty much a feather foot. In fact I mostly drive with the fuel economy displayed on the EVIC. I'm certain I am the oddball here.

The last point is likely the most important for my mileage. I have no idea about your driving style but I certainly purchased a Jeep and not a Ferrari. I typically go from 0 to sixty in around a half a minute. I do drive up to 80 frequently on I-25 (to just keep up with traffic) but most of my commutes are rural roads between 30 to 45 mph. Not a lot of stopping and starting. But of course, driving anywhere near metro Denver there are stop lights galore. Yet, I do enjoy the ESS silence however when stopped.

I have no easy silver-bullet answer for you. I'd be way pissed too if I was getting that kind of mileage. That's big truck kinda crap.

Are you experiencing misfires or any other DTC fault codes? Have you every had your engine professionally tuned or had an emissions inspection?

Something as simple as a bad or fouled O2 sensor would be pretty damn detrimental to mileage.

Also running larger than stock tires without calibration adjustment means that you are actualling travelling further in one wheel revolution to what the computer is expecting. So fuel injector pulsewidth management will typically supply more fuel per distance traveled since the engine is actually working a little harder to what it's sensing. You're true speed is actually higher than your indicated speed.

Using cruise control regularly at high speed with an improper tire diameter calibration will only exacerbate this problem since the speedometer error percentage increases (larger delta) with velocity.

So tackle some of the easier stuff first and work your way up. There has to be specific, objective reasons why your mileage is so low.

Are you a good candidate for driving a 4xe hybrid? Trade this thing in if you're unable to sleep at night.

Jay

Dammnnn you're running Colorado 93 ?
I've been running 85 (Colorado 87) happy as a clam with no issues.
I get the not wanting knock, but even at altitude the computer will recalculate with air density changes. Higher octanes simply aren't necessary for a naturally aspirated engine.

 

[jeepoch]

Dammnnn you're running Colorado 93 ?
I've been running 85 (Colorado 87) happy as a clam with no issues.
I get the not wanting knock, but even at altitude the computer will recalculate with air density changes. Higher octanes simply aren't necessary for a naturally aspirated engine.

John,

It's all about knock potential. Any knock (whatsoever) is in some way detrimental to your piston rings and cylinder surfaces. The Engine Control Module (ECM) will certainly 'react' to knock events and retard timing but only after-the-fact. Some damage has already been done.

So I do what I can to prevent knock from occuring in the first place. The reason I'm pretty sensitive to this paranoia is that in a prior life I developed the firmware algorithms and code for the Engine Controllers on Chrysler Lar Car, Small Car and Jeep Truck programs through the 2010 model year. This code included spark timing and knock detection. I pity those poor mules we destroyed while prototyping this software. Knock is anything but forgiving.

Even back then, knock was something that you tried to aggressively limit. It didn't take but a few really bad events to start worrying about warranty implications. A few extra dollars per fill-up goes a long way in greatly reducing knock probability. Higher octane is indeed worth every penny. Recall, the manufacturer recommends the cheaper stuff as a hedge towards a lower cost of ownership. But as they say, 'you can pay now, or much more later'.

Also be aware that while most knock is imperceptible by the driver, it doesn't take much especially over time, to start losing compression. Without adequate compression your piston is useless. Guaranteed with frequent knock you won't have one bad piston but six and an overall useless engine.

So go ahead and feed your JL grape juice if that makes you happy at the pump, I'll continue to run 91 or better. I got nearly 350K miles from my previous 3.3L. I'm hoping to do even better on this 3.6L.

Happy motoring,
Jay

 

[longfiredragon]

I rarely see below 22 mpg, and as much as 45 mpg or so. Oh wait I have the 2.0L Turbo.

Sorry,messing with you all. LOL.

 

[BXFXJeep]

2007 3.8 2dr JK MT
2015 3.6 4 dr JK MT
2018 3.6 JL AT

All were Sahara stock with various Rubicon take off wheels, and they all gave about 14mpg mostly city, I'm not easy with the pedal.

Highway long distance I got low 20s going usually 70mph with quite a bit of 80+ mph, this was mostly Toronto/ NYC, and a couple of Toronto / Miami, Toronto/Midwest.

2021 Sahara 4xe which has the 2.0T, just filled-up, I did 80 miles mostly city and that required 7 gallons.

But I did 530 miles on .

From what I vaguely remember, my 90 YJ was worse, and the 99 TJ was about the same as the JK/JL.

 

[joetimmons]

OP what gear ratio do you have?

 

[jeepdabest]

I love having longer range because I hate to stop on long trips. I had a handyman install a 100 gallon auxiliary gas tank and I can now go from Phoenix to DC on one tank!!

 

[MEski4x4]

OP what gear ratio do you have?

4.10s

 

[Joaquim]

I don't see any numbers out of wack. Here is a shot of my 2023 JLR, 35 GY Duratrac @32 psi and 4:88 gears.

Round trip, 175 mi, I 75, on cruise 70% of the time at 71 mph.

That's exactly what I get, BF K02 34.4, crappy 3.45 gearing, 4 door, metal bumpers, V6

 

[jack bauer]

15-17 MPG
3.6 etorque auto
AEV 2.5
37's with 4.56

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