2025 Jeep Gladiator and shifting issues

[ShadowsPapa]

Bought the truck in April 2025 and I always ran 93 octane in my vehicles.... This truck ran like garbage since day one!!!! Shifting is jerky from 6-7-8 and it feels like the converter locks up HARD. Rode like this for about 4k miles and decided to put 100% 87 octane in it.... Totally different truck!!! Smooth shifts and no hard lock ups. Dumped some ethanol 87 and still rides great, Last Wednesday I decided to try 93 again and the demons returned!!!! Burned through that tank and went back to 87 and clearing back up now!!! I do not get it?? I am in no means a rookie when it comes to mechanics (owned and worked on a good many of muscle cars) so it is not a placebo effect at all..... Anyone else have this issue???

Why in the world do you run 93 octane fuel in a modern vehicle that recommends only 87?

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[ShadowsPapa]

I have a 25 Glad Rubi also with no problem at 87, I’ve never put 93 in and based on this never will.

Why in the world would anyone run 93? It's a total waste of money.
It's not "better fuel" - all it does is resist self-ignition. If you don't have detonation, then you'd run 87. And in a 3.6 if you have detonation, you have an engine problem or oil consumption.

People simply don't understand gasoline or what octane even is.

 

[ShadowsPapa]

I suspect it is due to the limits of the Cam Phasers to retard timing enough to account for slower burning fuel that higher octane is composed of.

Octane doesn't burn slower. It simply resists self-ignition.
Same energy content, same burn.

I HAVE run 93 as an experiment - just for kicks, saw no real difference (and I was towing for part of that). No issues, but no gain either.

The cam timing isn't going to depend on how fast or slow a burn is - it has no real idea of that, there's no sensor telling it of burn completion, only oxygen content of the exhaust.
That will impact fuel mixture.

Imagine running 93 in an engine built for racing and high RPM - and having it burn slower......... ouch.


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The higher the number, the more difficult the fuel is to ignite. It does NOT mean the fuel burns any hotter or colder, or slower or faster. It was once thought that high octane burned “slower” and that was why it didn’t knock, but we now know that’s not true.

The reason for it, is because of the purity. Higher octane ratings have more complete strings of hydrocarbons and fewer “pieces”. Think of a container of cashews. You get a tub of “fancy whole cashews”. That’s like your premium or high octane. Most of the cashews in it are, in fact, whole. But there’s still some pieces, halves, etc. Now, take a regular tub of cashews. You will have a lot of whole cashews in the tin, but there will be many halves and pieces. And then there’s the tin literally labeled “cashew halves and pieces”. There will be whole cashews in there, but more pieces than whole. That’s your low octane.

That matters because complete strings of hydrocarbons have to be broken down before it can combust. A full string is harder to break down because the bond between atoms is stronger than a broken chain. A partial chain takes less heat to break apart, so it will ignite at a lower temperature and pressure. Once broken, they are all hydrocarbons, so they burn at the same speed.
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Research shows that the flame front generated in the combustion chamber has a set speed for Regular and almost exactly the same speed for Premium. There is a difference, but it is very slight. This is a requirement of commercial grade fuels for the public to use in piston engine aircraft and automobiles. Other racing car fuel blends can be quite different though. Confusion arises when ethanol is part of the fuel blend, because it takes more heat energy to turn it to vapour, so causes the engine to run cooler. There is negligible difference in the flame front speed of the blend though.

Premium high octane fuel resists any secondary ignition that may be caused by the compression increase plus the increased heat of the ignition. It does not burn slower, just resists having that second flame front. Regular low octane fuel in a high compression engine is affected by the ignition temperature and the sharp increase in pressure. This can cause a second flame front to develop away from the first. This has nothing to do with either a fast or slow burn, just a second place the flame front is moving across the air fuel mix. The problem comes when these two flame fronts converge, because a supersonic shock wave happens at the convergence. This is called detonation. Pre-ignition is a totally different thing.
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[AstroZombie]

I can't afford high octane but i can (in Arizona) i have not had any issue. My does shift very strangely at times. It just won't. It just wants to red line.

 

[ShadowsPapa]

I think the higher octane stuff comes from decades ago where gasoline sellers were trying to get people to spend more money, so advertised that their premium was better gas, cleaner, cleaned the engine and made it last longer and so on. Back then, perhaps.
Not today, especially with top tier gas.
Similar for the slower burning. That likely originated when lead was taken out and gasoline suppliers scrambled for ways to increase octane. A lot of things were tried and used, and back then, some really complex circular chains got used. However, without a big chemistry lesson here, those also left behind a lot of soot, and had other issues, carbon and so on.
The idea of the slow burn stuck, even with other compounds used to increase the octane in gasoline that have similar burn speeds to plain gas.
If higher octane gas caused running issues, I question the quality of the gas, not the octane level.

 

[blownbayou]

Why in the world do you run 93 octane fuel in a modern vehicle that recommends only 87?

Old gear head...... Cannot help myself

 

[blownbayou]

Why in the world would anyone run 93? It's a total waste of money.
It's not "better fuel" - all it does is resist self-ignition. If you don't have detonation, then you'd run 87. And in a 3.6 if you have detonation, you have an engine problem or oil consumption.

People simply don't understand gasoline or what octane even is.

I am well aware of octane and how it works...... My 2000 Ford Lighting had to be rebuilt TWICE due to detonation. Not because of octane, but because of WOT into OD (aerodynamics) and the second time the stock MAF could not keep up and leaned out the motor. With all the advancements nowadays (knock sensors and what not), running a higher octane is a waste in newer vehicles (agree with you). I have done it for so long. it is a hard habit to break unless I get what I had early this week.... I also had the head problem on my 2014 JK and had ran 93 as well. Now the wife's JL is the 2.0 Turbo and I know the book probably states 87, but it is a turbo so 93 goes in it without question. Peace of mind in a forced induction platform for a few cents more

 

[In3briatedPanda]

Should have asked Jeep if they would mind slipping you 20 bucks a day to supplement your fuel consumption

first person stated : just start you car earlier. i replied 'to warm up my transmission'? he eagerly stated 'Yes'. I should have just stopped there tbh.

I get some people are 'green' but that one made me scratch my head and lose faith in the dealer.

 

[MeanGreen]

I am well aware of octane and how it works...... My 2000 Ford Lighting had to be rebuilt TWICE due to detonation. Not because of octane, but because of WOT into OD (aerodynamics) and the second time the stock MAF could not keep up and leaned out the motor. With all the advancements nowadays (knock sensors and what not), running a higher octane is a waste in newer vehicles (agree with you). I have done it for so long. it is a hard habit to break unless I get what I had early this week.... I also had the head problem on my 2014 JK and had ran 93 as well. Now the wife's JL is the 2.0 Turbo and I know the book probably states 87, but it is a turbo so 93 goes in it without question. Peace of mind in a forced induction platform for a few cents more

I can understand running premium in the 2.0 since it's "recommended" but running 93 in an 87 octane recommended engine has zero benefits. That being said I've personally never heard of a vehicle running worse on premium fuel. That's very strange.

 

[Stan H]

first person stated : just start you car earlier. i replied 'to warm up my transmission'? he eagerly stated 'Yes'. I should have just stopped there tbh.

I get some people are 'green' but that one made me scratch my head and lose faith in the dealer.

Oh yeah I can see what ya mean

 

[ShadowsPapa]

I also had the head problem on my 2014 JK and had ran 93 as well. Now the wife's JL is the 2.0 Turbo and I know the book probably states 87, but it is a turbo so 93 goes in it without question. Peace of mind in a forced induction platform for a few cents more

That head issue was something else entirely.
We also have a JLU with a 2.0 turbo - 87 goes in it.
I checked in the Wrangler forums as well as other places after seeing what the book suggested - most who owned them were running 87 except in hot weather or when really loading it down. (book also talks of temperatures and loads for octane choice - and that makes total sense). No one had any issues, some having owned their 2.0 for quite a while.

93 is almost impossible to find around here, and that's ok - my 73 gets 91 and has had no trouble, my 70 got 91 with the built 390, no trouble (after I put in a better radiator, that is).
I did try to lower the compression a bit with lower heads, but then undid all of that with the cam, which ended up giving it higher dynamic compression. The math was a lower ratio, the reality was higher pressures.

A few cents more is like 60+ cents.

 

[blownbayou]

That head issue was something else entirely.
We also have a JLU with a 2.0 turbo - 87 goes in it.
I checked in the Wrangler forums as well as other places after seeing what the book suggested - most who owned them were running 87 except in hot weather or when really loading it down. (book also talks of temperatures and loads for octane choice - and that makes total sense). No one had any issues, some having owned their 2.0 for quite a while.

93 is almost impossible to find around here, and that's ok - my 73 gets 91 and has had no trouble, my 70 got 91 with the built 390, no trouble (after I put in a better radiator, that is).
I did try to lower the compression a bit with lower heads, but then undid all of that with the cam, which ended up giving it higher dynamic compression. The math was a lower ratio, the reality was higher pressures.

A few cents more is like 60+ cents.

South Louisiana.... Def hot weather :-(

 

[blownbayou]

That MEOW picture you have @ShadowsPapa is the business!!!!

 

[ShadowsPapa]

South Louisiana.... Def hot weather :-(

Been unusually hot here - but thankfully, this isn't the 5th year of drought, we've been getting rain otherwise we'd be in deep trouble.
We've had an unusual number of days in the 90s back as far as May. Weird for us. May is usually chilly.
Time for the corn sweat and 100% humidity days now. Dew point matching actual temperature........

 

[Chasm]

if the throttle lag is contributing to this as well

The throttle lag drives me nuts.

Usually an octane boost doesn't cause issues, it's just a waste, but I suppose there might be the rare occasion that it messes with newer engines that try to adjust things like timing based on conditions.

Higher octane is used to prevent "pre-detonation" in higher compression engines from the heat and compression, but spark should light the fire no matter the octane.

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