24+ mpg after 6 weeks on the road

[Sazabi19]

Well. Hit 5k miles today and my mileage hasnt improved. This is the only vehicle ive driven That wasnt up-armored that you could set the cruise control at 65 and watch your mileage plummet.

on mixed driving of highway and interstate ive maxed at 20.2 with 93. Interstate only at 65-75 is high 17’s low 18’s. I expected mileage to not be great but this is absurd. The sahara I rented in co got me 24.5 all mixed to include 4lo for the week.

as it sits, my mojave is getting 4-5mpg worse than my Ram 2500 did. It just doesnt have the power to turn mud terrain tires. Its always having to hunt 5,6,and 7 gear and comes out of 8th almost as soon as it drops into it. Any hill at all and its kicking down gears and mileage plummets to 10-14 depending on incline.

im on the fence as to whether or not trying to regear it or just dump it for something else. I like everything else about it, just needs more power. And im not about to dump 10-30k on a blower or a v8 conversion. Gearing down would probably help mileage, but it isnt cheap.

Why are you using 93? Our truck doesn't call for it so just wondering. This truck is super non-aero so I've noticed going above 60 really starts to tank mileage. Also, have you taken into account the transition from warm fuel blend to winter? The winter blend tends to lose 3mpg+ easy. Plus vehicles don't take to cold weather all that well. Being in VA I assume you know this but just checking to see if you had though about it at all.

As of right now my gauge (only) has been showing about 19-20mpg average my last few trips as opposed to the 22+ it was showing when it was warmer. Even on a warmer day in general (on the same winter gas) I see a nice increase in mileage.

@ShadowsPapa Is that just according to the gauge or is that after hand calculation? I'll also pose the same questions to you that I did above about winter fuel blend + cold weather. I assume you guys are dropping in IA right now.

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[BAT]

I have noticed the same thing since my 3rd dealership oil change, normally I lose 2-4 mpg for first tank of gas this time I lost 6+ MPG and still trying to work it back up to 23+ MPG but haven't in over 4 refuelings.

Interesting as I just had my first oil change at 5000 miles and I am at around 7000 now. I guess I didn't put to much into it but I did notice my gas mileage dropped off by about 2-3 mpg after the oil change from what I was getting. My driving habits are the same

 

[Blade1668]

Interesting as I just had my first oil change at 5000 miles and I am at around 7000 now. I guess I didn't put to much into it but I did notice my gas mileage dropped off by about 2-3 mpg after the oil change from what I was getting. My driving habits are the same

I'm over 20k and each oil change I noticed a drop in MPG this time it's not got back to prior MPG yet and a larger drop. I did just buy a new air filter to replace it and see if it helps. I have seen that make a difference in my other Jeeps with K&N filters. I've decided not to get a K&N filter for it... Yet I've heard some negative things about them but nothing personal in my 4 Jeeps with one.

 

[ShadowsPapa]

I have noticed the same thing since my 3rd dealership oil change, normally I lose 2-4 mpg for first tank of gas this time I lost 6+ MPG and still trying to work it back up to 23+ MPG but haven't in over 4 refuelings.

I have mixed feelings. As a former mechanic myself, and still today doing odds and ends, and dipping into the older control systems and trying hard to feebly keep up withe current, I can see why a PCM flash can be preventative. I mean, if you see that the initial version results in some having troubles - and they trace SOME of those troubles (including misfires - or worse) to the PCM code, then do I refuse any updates? Naw, no thanks, I'll take my chances that you don't have to rebuild this engine.
And keeping in mind I DID complain about the transmission hunting badly, it being a real pooch towing my empty trailer, or even driving in NW Iowa's more flat land than what's around me - it shifted literally every few seconds even on what I consider minor hills - some suggested resetting the controls and making it learn again. Do I refuse the flash even knowing I bitched about how it shifted and how piss-poor it was towing on I80 between Des Moines and Omaha?
Or do I keep complaining about it - refusing a flash?
The MPG was a big plus. I was hoping for better than my WJ and better than my Silverado.
It was doing better than either - now it's better than the Chevy, about the same as the WJ.
So it's a mixed thing - I'm happy for the better shifting....... and hopeful that the flash may prevent the engine issues, misfires, and that it results in a better towing experience.
I get why dropping the shifting from granny mode, shift soon, downshift one gear only when it lugs and going more to a sport mode shift pattern would drop mpg.
I may ask the dealership next visit if they've had complaints, or see if they have an opinion, but will phrase it more as a "I was wondering" - as in I'm curious, what do you think, than "I don't like this" in a complaint format.
If any of that makes sense......

 

[DreamedofaJeepSomeday]

I have mixed feelings. . . . do I keep complaining about it - refusing a flash?

If any of that makes sense......

Do they tell you they need to do a flash before going ahead with it? Give you an choice?

 

[ShadowsPapa]

Why are you using 93? Our truck doesn't call for it so just wondering. This truck is super non-aero so I've noticed going above 60 really starts to tank mileage. Also, have you taken into account the transition from warm fuel blend to winter? The winter blend tends to lose 3mpg+ easy. Plus vehicles don't take to cold weather all that well. Being in VA I assume you know this but just checking to see if you had though about it at all.

As of right now my gauge (only) has been showing about 19-20mpg average my last few trips as opposed to the 22+ it was showing when it was warmer. Even on a warmer day in general (on the same winter gas) I see a nice increase in mileage.

@ShadowsPapa Is that just according to the gauge or is that after hand calculation? I'll also pose the same questions to you that I did above about winter fuel blend + cold weather. I assume you guys are dropping in IA right now.

One reason I'm not jumping up and down hard and complaining to a dealer - we HAVE entered winter. Highs here MAY hit low 20s, it's 3:30 and I think it may have just hit 22. It was 17 on much of our morning drive. So..........
I have verified the odometer and speedometer using two methods and it's SPOT ON - I mean it agrees absolutely to the tenth of a mile over a nearly 20 mile trip with my Garmin and my phone GPS both. After a trip to town and back, the odo, phone and Garmin were still in total sync down to the tenth of a mile. And I track how many gallons goes in over time (not just a single fill)
I don't know what they do to the fuel for Iowa........ diesel is absolutely different - I know from my farming days the diesel varied.
And these trucks are pulling around and spinning extra driveline parts in this cold weather. Even with FAD, you are turning the spider/carrier side gears in the carrier with the left front axle - that's extra cold metal in cold lube.
Spring will tell for sure. Cold weather does impact MPG.
It was lower BEFORE cold weather hit - we had a warm fall here. In fact, my shop hardly used any LP in the 36' infrared heater and our home electric bill was a fair amount less than last fall. So it did drop even before winter set in - it's worse now for sure. I bet the cold of the last few days has dropped it about 2 mpg from the low the reset caused.

 

[ShadowsPapa]

Do they tell you they need to do a flash before going ahead with it? Give you an choice?

Yes. They say "I see your PCM is due for a flash" and the paperwork listed it as a recall flash.
But having read several TSBs on the PCM issues, and all of the engine troubles - and knowing my auto transmission needed a kick in the butt - I almost always say "do whatever".

 

[DreamedofaJeepSomeday]

Yes. They say "I see your PCM is due for a flash" and the paperwork listed it as a recall flash.
But having read several TSBs on the PCM issues, and all of the engine troubles - and knowing my auto transmission needed a kick in the butt - I almost always say "do whatever".

Well, I have a manual and exceptionally good fuel economy, no issues with anything, so a flash for me will be a hard sell.

 

[Blade1668]

Overall I'm good with a drop in MPG to a point if it keeps the drive train intact and long lasting aka if I'm still not throwing $ at it to keep it running after 200 K plus, but I've been lucky (?) with my Jeepsengines, transmission, T-case, axles ect. My retired XJ I have flogged the H### out of it and got ok MPG about 20, my MJ has been ran really hard in Europe on Autobahn's it got great MPG before I had it there. My LJ has been stellar in reliable of just needed normally wear and tear replacement stuff. But all of them are 4.0 engines.
But I don't change vehicles like some change their socks..

 

[KurtP]

Why are you using 93? Our truck doesn't call for it so just wondering. This truck is super non-aero so I've noticed going above 60 really starts to tank mileage. Also, have you taken into account the transition from warm fuel blend to winter? The winter blend tends to lose 3mpg+ easy. Plus vehicles don't take to cold weather all that well. Being in VA I assume you know this but just checking to see if you had though about it at all.

As of right now my gauge (only) has been showing about 19-20mpg average my last few trips as opposed to the 22+ it was showing when it was warmer. Even on a warmer day in general (on the same winter gas) I see a nice increase in mileage.

@ShadowsPapa Is that just according to the gauge or is that after hand calculation? I'll also pose the same questions to you that I did above about winter fuel blend + cold weather. I assume you guys are dropping in IA right now.

i get a full mpg higher on 93 than i did on 87

i think 87 is too low of an octane for the compression ratio of these engines. Opinions vary.

i may regear and remap; but im apprehensive to flash the pcm on account of warranty.

 

[ShadowsPapa]

There's guys running 87 pump gas on 10:1 and a bit higher with old-school engines from the early 70s. If you keep the burn FAST (a quick burn chamber cuts detonation) and keep swirl to keep the mixture in motion once in the chamber and have a good quench you can run pretty high compression ratios. There's also dynamic vs. static compression - you can have a given compression ratio "calculated" that in practice is either higher or lower, depending on the cam grind.
I dropped the compression ratio on my 390 by putting on larger chamber heads and then put in a cam that raised it right back up again.

Timing and other factors on these engines is only going to go so far regardless of the octane fuel.
Since octane is purely and only resistance to self-ignition, timing will only advance so far if there's a knock from detonation, and then it will only go so much farther if there's no knock. You advance timing ONLY so far as to get peak combustion pressures to happen at about 14-16 ATDC. Any more advancement of timing is counter-productive and likely destructive. Those who say "advance it until it pings then back off just a bit" are idiots. And I mean that just as harsh as it sounds.
Timing changes to keep peak combustion pressures happening at the same number of degrees ATDC based on engine speed and load conditions - since the burn takes TIME, it's a controlled process and not an explosion as some lame, non-engineer written books and articles claim. I've even seen PM write about the "explosion in the chamber" what a hoot.

 

[KurtP]

after reading more i think they pulled a bunch of timing out of the tune with the pcm reflash. It would explain why power is down and mileage is worse; and that would fix some misfire issues.

all so it can run on 87.....

im still not confident in the pulsar; and livernois charging over $200 to crack the ecu before they charge another $5-600 to tune it is priced too high.

might be worth a class action lawsuit against jeep. They claim what? 21-22 highway? Getting 18 is 20% off.

 

[ShadowsPapa]

after reading more i think they pulled a bunch of timing out of the tune with the pcm reflash. It would explain why power is down and mileage is worse; and that would fix some misfire issues.

all so it can run on 87.....

im still not confident in the pulsar; and livernois charging over $200 to crack the ecu before they charge another $5-600 to tune it is priced too high.

might be worth a class action lawsuit against jeep. They claim what? 21-22 highway? Getting 18 is 20% off.

Power down? No! Not for me - the opposite! It's actually more sporty driving it and there's NO power loss.
Backing timing off won't fix misfire, either. The misfire issues appear to be more related to the EGR system and other things.
These run great on 87 octane.

The EPA numbers are not a claim and they have a disclaimer in there. No one is ever going to sue and mention mpg - they'd be laughed out of the room.
MPG numbers also rely on bone-stock factory configurations. Go changing anything, and you have just negated any claim that "Jeep lied about mpg".
Besides, your area's elevation and terrain, your personal driving habits and more contribute to mpg as much as anything. To counter your claims, Jeep only has to take stock trucks off the line, run them on a test track at normal speeds, set the cruise, and prove their numbers.

I CAN get 22+ mpg on the highway still if I limit speeds to 55-60. It's the other areas, my mixed driving, where you rely on the lower gears and the shifting sequencing that mine has dropped, or, speeds over 65. And that makes sense - their tests for mpg are not done at 75+ and anyone who drives over 70 and expects great mpg is being silly.

I've never had any issues with 87 octane in any modern vehicle - nothing since about 1994 or so.
My JT has NOT lost power with the flash - the opposite - and with power and sportier shifting, you'd expect some mpg loss under certain conditions.
Mine shows zero indications of timing being retarded.
Having tuned hundreds of vehicles (likely many hundreds) over the last 45 years, advanced timing does not lead to misfires unless you REALLY take it to the extreme - where damage happens, so there's no reason for them to "back timing off to fix a misfire". You are more likely to have rougher running and misfires with retarded timing - and more heat. Their misfires, if you read the technical explanations, aren't related to timing, nor would they be.

 

[Sazabi19]

Not sure where you guys live but stepping up to 93 in my area is like an extra 50 cents. That's too much an extra mile for me. I would run a tank of 93 through my Cadenza once a year or so because it has some extra detergents in it but that was about it. I figured I wasn't burning it all so it was just a waste ultimately. I was under the assumption that my engine wasn't running hot enough to burn it all. I also put Techron in my tank every other oil change to help with carbon build up as recommended in my manual (very sooty engine).

 

[KurtP]

Power down? No! Not for me - the opposite! It's actually more sporty driving it and there's NO power loss.
Backing timing off won't fix misfire, either. The misfire issues appear to be more related to the EGR system and other things.
These run great on 87 octane.

The EPA numbers are not a claim and they have a disclaimer in there. No one is ever going to sue and mention mpg - they'd be laughed out of the room.
MPG numbers also rely on bone-stock factory configurations. Go changing anything, and you have just negated any claim that "Jeep lied about mpg".
Besides, your area's elevation and terrain, your personal driving habits and more contribute to mpg as much as anything. To counter your claims, Jeep only has to take stock trucks off the line, run them on a test track at normal speeds, set the cruise, and prove their numbers.

I CAN get 22+ mpg on the highway still if I limit speeds to 55-60. It's the other areas, my mixed driving, where you rely on the lower gears and the shifting sequencing that mine has dropped, or, speeds over 65. And that makes sense - their tests for mpg are not done at 75+ and anyone who drives over 70 and expects great mpg is being silly.

I've never had any issues with 87 octane in any modern vehicle - nothing since about 1994 or so.
My JT has NOT lost power with the flash - the opposite - and with power and sportier shifting, you'd expect some mpg loss under certain conditions.
Mine shows zero indications of timing being retarded.
Having tuned hundreds of vehicles (likely many hundreds) over the last 45 years, advanced timing does not lead to misfires unless you REALLY take it to the extreme - where damage happens, so there's no reason for them to "back timing off to fix a misfire". You are more likely to have rougher running and misfires with retarded timing - and more heat. Their misfires, if you read the technical explanations, aren't related to timing, nor would they be.

goodness. Ok.

i have to be honest here. Im calling bullshit on your experience. You are flat wrong on almost everything you post regarding engine calibration in every single thread i have read. You either didnt actually do it; or you were doing it at such a low threshhold that you were getting away with it.

this is another thread where you are flat wrong on almost everything you posted; or are confusing your vehicles ability to turn passenger car tires to others turning larger heavier mid terrain tires.

1- you dont know if you lost power or not because you didnt measure it before and after. Period. I speculate that you MIGHT have because the gearbox is having to work harder and your mpgs dropped. In either case, the issue of power lacking was an absolute statement on my part because the 3.6 as programmed and as geared cannot effectively turn mud terrain tires even with 4.10 gears. I get worse mileage in Virginia than i did with the Sahara in colorado. By over 20%. I get worse mileage in my gladiator than i did in my ram 2500. if the motor cant make enough power to turn the drivetrain, it has to down shift and dip into throttle. To keep the motor from detonating you need to add fuel and cut timing. Bad tuning will consume more fuel than efficient tuning. Power and efficiency come hand in hand. The reduction of power of the jt/jl 3.6 from other modes is (from what ive read)from lack of thermal management and them looking to hedge some safety into crawling at high heat.

2- misfires. You CAN induce misfire and detonation through bad cylinder timing. and anyone who has really tuned a vehicle knows this. You dont know what changes where made to the pcm, because you didnt look at data logs before and after. Period. I said my speculation was they adjusted timing because there were also reports of detonation and a couple motor failures that COULD be detonation related. I dont know exactly what they did, i only see the incidents reported and the post tune results. Is it 100%? Absolutely not. But ive been doing this long enough that im putting my money there. Other egr or other pcm issues resolved may have been part of the problem or separate; but its rare to have a singular issue be the sole reason for a pcm update, and what they name it or cite as the reason can never be taken as absolute.

3- i dont expect to get “great mileage” from driving a brick 70mph. Im frustrated that my ram 2500 is getting over 20% better mileage than the jeep does; and im more frustrated that the jeep cant even get close to what theyve claimed under any circumstance ive driven in. Alot of this could be fixed with some better engine management and more intake. Im speculating here but i also wonder if the exhaust design is causing higher egt‘s and this is part of the reason they had to detune it. Im just on the fence as to whether or not to do It.

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