3.6 - For Those Running Premium Fuel

AnnDee4444

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do I trust the designers of the machine, who lose money when the machine fails?
Not if it's outside of warranty...
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Livernois Motorsports

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Not if it's outside of warranty...
Exactly, the amount of engineering that goes into targeting a failure per sold unit ratio is staggering, so if the base warranty is 60k miles, you have a very low number of failures targeted in this mileage range. Then you have a window of available extended warranty with it's own approved failure rate. Then past this it can literally be the sky's limit.

There are a crazy amount of items like this that seem to fail shortly off warranty for all manufacturers. While it's not the "planned obsolescence" people think of, there absolutely is a real amount of engineering dedicated to reducing warranty failures within a given timeframe, but after that it's barely a second thought on if it fails or not.

Again, this is something all OEM's are guilty of. Look at pentastar rocker issues. almost all of them happen off warranty, but some don't. This is a perfect example of this.

Every part of a vehicle is a constant battle between initial cost, and post sale cost. But the more complex the system, the more of this constant battle happens.
 

TheRaven

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Not if it's outside of warranty...
Every single JL comes with a warranty. But it's not only warranty claims at stake. All automakers want their products to be known as high quality and reliable. They lose arguably more money on perception than on actual problems. Expectations are that a high quality modern vehicle can go at least 100k miles without major issues. When it comes to internal engine issues, there should be none...ever. If it were true that running 87 would create a high risk of internal engine problems at any mileage, you bet your ass they'd be telling you to run premium... they do exactly that on the SRT cars in fact.
 

AnnDee4444

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Every single JL comes with a warranty. But it's not only warranty claims at stake. All automakers want their products to be known as high quality and reliable. They lose arguably more money on perception than on actual problems. Expectations are that a high quality modern vehicle can go at least 100k miles without major issues. When it comes to internal engine issues, there should be none...ever.
The manufacture doesn't get to pick and choose what will cause issues, break prematurely, or make it through that warranty. It wasn't a conscious decision to design a clutch that explodes, dead-spot steering, and possibly tuning that requires constant ignition retarding to reduce detonation.

They make mistakes, or cut corners a little too close. Some make it past warranty, some cause fires that burn the vehicle down in under 10,000 miles.

If it were true that running 87 would create a high risk of internal engine problems at any mileage, you bet your ass they'd be telling you to run premium...
I doubt it. Have you seen the number of people that bitch & moan about the 2.0 taking premium fuel? It's frequently listed as one of the reasons why some people avoid it. Hell, isn't the fact that we've argued for 15 pages evidence enough that there are some people that will never accept spending more than the bare minimum on fuel? I highly doubt that there will ever not be at least one Wrangler offered that takes standard grade fuel (at least until the EV takeover).
 

Caleb75

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I have switched over to non-ethenol 87 octane. I had a spark knock or low load " rattle". It was better when I used higher octane fuel. I decided to try non-ethenol with a bottle of Amsoil PI Performance Improver. It is significantly better with non-ethenol gas. So, I now fill up with non-ethenol. My ride is a 2020 JLU Sport Altitude 3.6 automatic.
 

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If it were true that running 87 would create a high risk of internal engine problems at any mileage, you bet your ass they'd be telling you to run premium... they do exactly that on the SRT cars in fact.
THIS. FCA can't make the statement of "running higher than 87 octane will provide no benefits", without documents to prove this (this includes MPGs, power output, and engine life). I've learned the hard way in business/manufacturing that ANY claim a company dare makes that's a selling point gets checked by FTC regulator assholes who are dying to bust you on it (for their resumes), even "this product won't hurt the Earth's molten core". If you make the claim, they'll call you on it and you have to prove it before it's even allowed to be published. If they did pull off an "oopsy", or lie here, they'd be opening themselves up to a slam dunk HUGE class action lawsuit, regardless of it being in or out of warranty. Even if it only impacted the life of the engine by 2%. For the # of engines sold and penalty that they'd incur, any major firm would eat this up and attack.

But whatevs, run what fuel you want. I will. The engine doesn't seem to be falling apart by the masses yet and we know most are likely running 87, as the manual says to.
 

TheRaven

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The manufacture doesn't get to pick and choose what will cause issues, break prematurely, or make it through that warranty. It wasn't a conscious decision to design a clutch that explodes, dead-spot steering, and possibly tuning that requires constant ignition retarding to reduce detonation.

They make mistakes, or cut corners a little too close. Some make it past warranty, some cause fires that burn the vehicle down in under 10,000 miles.
Agreed, and these are the things that fall under the "should not break in the first 100k miles". But the internals of a 3.6l pushrod or DOHC V6? Old as dirt. Thus, this is an engine that must go the life of the vehicle without internal issues. Failing to do that, at scale, would be a disaster far more costly than any warranty. They will not be taking any chances on that front.

I doubt it. Have you seen the number of people that bitch & moan about the 2.0 taking premium fuel? It's frequently listed as one of the reasons why some people avoid it. Hell, isn't the fact that we've argued for 15 pages evidence enough that there are some people that will never accept spending more than the bare minimum on fuel? I highly doubt that there will ever not be at least one Wrangler offered that takes standard grade fuel (at least until the EV takeover).
More than 90% of Wrangler buyers don't even know what octane the engine requires until they go to fuel up their new JL for the first time. I'd wager good money that a huge chunk NEVER do...and just put 87 in it.

FCA does state in the manuals of SRT cars that 91 octane should be used. They do it in the 2.0l Wrangler too. So why not for the 3.6l? Because the people who designed and built the engine, and put hundreds of thousands of test miles on it, found that premium fuel is not necessary.

This argument needs to be allowed to die.
 
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AnnDee4444

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Agreed, and these are the things that fall under the "should not break in the first 100k miles". But the internals of a 3.6l pushrod V6? Old as dirt. Thus, this is an engine that must go the life of the vehicle without internal issues. Failing to do that, at scale, would be a disaster far more costly than any warranty. They will not be taking any chances on that front.
Just like the clutch.

More than 90% of Wrangler buyers don't even know what octane the engine requires until they go to fuel up their new JL for the first time. I'd wager good money that a huge chunk NEVER do...and just put 87 in it.
Yeah, and exactly 69.420% of Wrangler buyers get told the octane requirements at the dealership when they make the purchase but forget when signing the paperwork. Source? Trust me bro.

So since there is slight power to be gained with 91 octane, why wouldn't they change one number in the owner's manual and have the 3.6 perform better on the test drive? I mean "91" probably uses less ink than "87", and they literally have nothing to lose since apparently 90% don't know or care what grade of gas they pump... right? Or maybe they know that their market demands simple products and keep certain things around even though they were more of an afterthought for the vehicle design... like the manual transmission.

FCA does state in the manuals of SRT cars that 91 octane should be used. They do it in the 2.0l Wrangler too. So why not for the 3.6l? Because the people who designed and built the engine, and put hundreds of thousands of test miles on it, found that premium fuel is not necessary.
And apparently never make mistakes, like the clutch.
 

PsychoTrucker81

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Agreed, and these are the things that fall under the "should not break in the first 100k miles". But the internals of a 3.6l pushrod V6? Old as dirt. Thus, this is an engine that must go the life of the vehicle without internal issues. Failing to do that, at scale, would be a disaster far more costly than any warranty. They will not be taking any chances on that front.



More than 90% of Wrangler buyers don't even know what octane the engine requires until they go to fuel up their new JL for the first time. I'd wager good money that a huge chunk NEVER do...and just put 87 in it.

FCA does state in the manuals of SRT cars that 91 octane should be used. They do it in the 2.0l Wrangler too. So why not for the 3.6l? Because the people who designed and built the engine, and put hundreds of thousands of test miles on it, found that premium fuel is not necessary.

This argument needs to be allowed to die.
The 3.6 Pentastar isn’t a pushrod engine…it’s DOHC. You keep pontificating and arguing on the octane subject, yet you don’t even know the general design of the engine you are arguing about??
 

Dkretden

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I just follow the owners manual. I follow it for things like type of oil, oil change frequency, and gas octane.
 

TheRaven

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The 3.6 Pentastar isn’t a pushrod engine…it’s DOHC. You keep pontificating and arguing on the octane subject, yet you don’t even know the general design of the engine you are arguing about??
It's irrelevant to the conversation. OHC is even older.
 

Ridgway Jeeper

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Modern control systems adjust the calibration for altitude, so it measures BARO almost continuously and adjusts the calibration, both fueling and spark (as well as other items) so they add power in because the less dense air typically allows for more timing, because of that though the octane requirements don't change nearly as much as older vehicles used to.
I bought my wife a new Rubicon 3.6 manual a little over a month ago. We live at altitude and operate the Jeep between 6000-10,000 feet 95% of the time, it will likely never go below a mile high as it is our around home vehicle.

Our mid grade is 87, as mentioned by others and that is what I have been running in it. After reading a fair amount of this discussion, it is pretty clear to me that going with the available 91 which all has 10% ethanol here may be to our advantage in the long run, and even in daily driving.

The Jeep has just under 2000 miles on it now and from my reading has likely adopted a long term knock control strategy. So if we start running premium exclusively what is the best way to get the ECM to stop pulling timing and start taking advantage of the higher octane fuel? Do we just start running it and wait? Does simply disconnecting the battery for a period of time cause it to reset?

I really appreciate the insight you have provided here. I must say that those who think the manufacturer has the consumers best interest in mind here is a bit humorous. Kind of like thinking the government has your back... Thanks for providing the info, it has convinced me that going to the better grade of fuel is advantageous.
 

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It's irrelevant to the conversation. OHC is even older.
LOL!

Don't you mean the flathead is even older? Again, you show you don't understand even the basics of engine design and operation. I will try one more time to explain the basis for this argument.

Every engine has an ideal time during the compression stroke to "light the fire." Doing so results in peak cylinder pressure occurring just as the piston reaches top dead center, creating the most power and having the greatest fuel efficiency. The time of the spark depends on a number of factors such as RPM and manifold pressure but NOT on octane.

If the fuel has insufficient octane the engine will knock which is bad. So the spark is delayed to prevent knock but this decreases peak cylinder pressure and thus both power and efficiency. So the question is, how much octane is needed for the 3.6? The answer depends on the altitude you live at and your driving style. If you live in Colorado or if you hypermile the manifold pressure will be low and 87 octane is fine. But if you live at lower altitudes and occasionally "get on it" then you should be running higher octane.
 

MrMischief

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FCA spoke, they were questioned, they spoke again, they were questioned again, and they spoke again. There is no ambiguity on where they stand on the proper octane for the 3.6l.
Can you source where they've spoken multiple times on this? Just wanting to see what they say for myself. Living at elevation where regular gas is 85 octane I do find ambiguity in the owners manual of every vehicle I've owned. They all read something like "use regular (87 octane) fuel". Well which is it? Regular or 87 octane? because here those two are not the same.
 

TheRaven

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Can you source where they've spoken multiple times on this? Just wanting to see what they say for myself. Living at elevation where regular gas is 85 octane I do find ambiguity in the owners manual of every vehicle I've owned. They all read something like "use regular (87 octane) fuel". Well which is it? Regular or 87 octane? because here those two are not the same.
You can find it easily by searching the forum. There are countless threads referencing it. This is a long dead horse that keeps getting new rounds of beatings.

They put 87 octane in parenthesis to define what they consider "regular". It is regular in most of the contiguous US. For you, 87 is more like 89 for us lower folk.
 
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