3.6 engine and 87 octane a no-no

[WhereRU_A-A-Ron]

My cousin’s sister’s boyfriend’s dad’s uncle’s uncle built racin’ engines for them NASCAR race cars. He said that anything below 120 octane is just water and gonna rot your engine from the inside out.

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[Gorilla57]

Octane boosters are snake oil and don't do squat. If you really "need" higher octane, you have use 89/91/93 out of the pump and if you need more, you have to add race fuel concentrate or run unleaded race gas.

 

[Reseg]

I still can't get over them saying that there is no benefit on these engines to running premium, but then the very next sentence they say you may experience audible knock while running 87 but that it's cool. You know what resists knock? Higher octane gas, sounds like a benefit to me.

Where does it say that? The below image is all I see. The only mention of them saying a light knocking sound is no cause for concern doesn't reference it being from using 87, and also doesn't seem to be referring to actual ping/detonation, but simply a light knocking sound, which can come from normal operation of parts that can make ticking, knocking, and clicking sounds normally. If your Jeep is actually having detonation problems, something is wrong with it. The knock sensor should pick it up and likely throw a code if it's actually a problem. That's different from the 2.0 and other motors/ECUs that are tuned to adjust to different fuels and run differently.

I'm not pretending to know everything, but I spent years tuning and racing, sitting on dynos while adjusting timing, A/F ratios, and boost by RPM, while watching EGTs and tons of instruments, of course looking for detonation. I think we may have some people here jumping to conclusions when they hear a noise, about it being actual knocking (detonation).

IMO, if the 3.6 was truly having detonation issues with 87 octane, this would've easily been exposed already by the tuners who are putting out turbo/supercharger kits. They're sitting on dynos and watching every metric of the motor, which would easily show this. I highly doubt they'd be quiet about it, in fact they'd probably use it as a marketing angle for a reason to get their tune, so your engine lives a longer life.

If the engine is tuned for 87, it will run best on 87. If it's knocking, there's something wrong with it, so get it fixed. Putting in higher octane will likely hurt, not help the life of the motor, except in the case of it truly knocking, it may help temp bandaid it. People talk about going to higher octane "to be safe", do what you want, I get it, but know all the talk of "bad gas" isn't a matter of being more likely with 87, it's actually a higher chance of having a problem with higher octane due to it being purchased less and sits longer at most stations.

 

[Creeker]

When one looks at what pinging (AKA, pre-denotation, engine knock, etc.) it is the fuel igniting before it should. Therefore, the gas/fuel mixture pre-denotates, which means the the detonation is occurring too soon. The pre-detonation is occurring as the piston is still coming up, which means the early detonation is tying to force the piston down while the piston is coming up. Not a good thing.

Therefore, the pre-detonation is reducing the potential power an engine can produce if it had been running a higher octane. Now how much power, is lost during pre-detonation, who knows. The amount of damage caused by occasional lighting pinging, who knows.

For me, just don't want the pre-detonation to occur. Especially at low RPM when the Jeep is trying to climb/crawl an obstacle. Enough stuff to worry about when wheeling and don't to hear that irritating pinging sound. Figure we spend enough $$ on our rigs and upgrading them that a little more $ for better gas is a drop in the bucket.

We ask our Jeeps to do a lot for us. Running 93 octane is the least I can do to help out the Jeep do its job.

Just my $0.015 worth.

 

[OldGuyNewJeep]

If the engine is tuned for 87, it will run best on 87. If it's knocking, there's something wrong with it, so get it fixed. Putting in higher octane will likely hurt, not help the life of the motor,

Running 93 octane is the least I can do to help out the Jeep do its job.

 

[Bruce Willys]

Where does it say that? The below image is all I see. The only mention of them saying a light knocking sound is no cause for concern doesn't reference it being from using 87, and also doesn't seem to be referring to actual ping/detonation, but simply a light knocking sound, which can come from normal operation of parts that can make ticking, knocking, and clicking sounds normally. If your Jeep is actually having detonation problems, something is wrong with it. The knock sensor should pick it up and likely throw a code if it's actually a problem. That's different from the 2.0 and other motors/ECUs that are tuned to adjust to different fuels and run differently.

I'm not pretending to know everything, but I spent years tuning and racing, sitting on dynos while adjusting timing, A/F ratios, and boost by RPM, while watching EGTs and tons of instruments, of course looking for detonation. I think we may have some people here jumping to conclusions when they hear a noise, about it being actual knocking (detonation).

IMO, if the 3.6 was truly having detonation issues with 87 octane, this would've easily been exposed already by the tuners who are putting out turbo/supercharger kits. They're sitting on dynos and watching every metric of the motor, which would easily show this. I highly doubt they'd be quiet about it, in fact they'd probably use it as a marketing angle for a reason to get their tune, so your engine lives a longer life.

If the engine is tuned for 87, it will run best on 87. If it's knocking, there's something wrong with it, so get it fixed. Putting in higher octane will likely hurt, not help the life of the motor, except in the case of it truly knocking, it may help temp bandaid it. People talk about going to higher octane "to be safe", do what you want, I get it, but know all the talk of "bad gas" isn't a matter of being more likely with 87, it's actually a higher chance of having a problem with higher octane due to it being purchased less and sits longer at most stations.

Page 369 of the 2020 owner's manual:

There is nothing wrong with the engine according to them if you're hearing 'light knocking', but the engine knocking loudly enough to be heard is not optimally timed combustion very obviously. You have experience tuning so you know what happens to fueling strategies as knock control increases.

 

[Reseg]

There is nothing wrong with the engine according to them if you're hearing 'light knocking', but the engine knocking loudly enough to be heard is not optimally timed combustion very obviously. You have experience tuning so you know what happens to fueling strategies as knock control increases.

Woah, that's worded a little differently (in a not so good-sounding way lol) than my 2021 manual, which is where I took my pic from (the PDF version they sent me). I could see where that could be read as it being a result of the 87 octane that there's knocking, maybe that wasn't intentional and why they updated it to what mine says. I still think they're referring to normal knocking sounds, not not actual detonation, but that sounds bad to read that way. Surely nobody would consider detonation to not be a concern, especially a manufacturer!

 

[chacomaya]

When one looks at what pinging (AKA, pre-denotation, engine knock, etc.) it is the fuel igniting before it should. Therefore, the gas/fuel mixture pre-denotates, which means the the detonation is occurring too soon. The pre-detonation is occurring as the piston is still coming up, which means the early detonation is tying to force the piston down while the piston is coming up. Not a good thing.

Therefore, the pre-detonation is reducing the potential power an engine can produce if it had been running a higher octane. Now how much power, is lost during pre-detonation, who knows. The amount of damage caused by occasional lighting pinging, who knows.

For me, just don't what the pre-detonation to occur. Especially at low RPM when the Jeep is trying to climb/crawl an obstacle. Enough stuff to worry about when wheeling and don't to hear that irritating pinging sound. Figure we spend enough $$ on our rigs and upgrading them that a little more $ for better gas is a drop in the bucket.

We ask our Jeeps to do a lot for us. Running 93 octane is the least I can do to help out the Jeep do its job.

Just my $0.015 worth.

What you're saying is basically true, but my understanding of what you are describing as "pre-detonation" is actually pre-ignition = the charge being ignited by something prior to the spark firing. Unlike normal combustion, where the spark plug creates flame kernel that spreads out with an ever growing flame front, detonation is a completely different thing, and is what we hear as pinging or knocking. Detonation occurs after normal ignition, or after pre-ignition. It is the instantaneous explosion of the entirety of the remaining unburned charge (after ignition or pre-ignition) caused, for example, by using fuel that has too low an octane rating. Pre-ignition and detonation both cause damage. Pre-ignition without detonation results in damage to the piston crown as the piston tries to compress an already high-pressure, burning mixture. Detonation creates supersonic shock wave(s) that slam against the piston and cylinder walls and, among other things, scour away the boundary layer that helps insulate the piston and cylinder walls from the heat of combustion, potentially leading to overheating in addition to the physical stress caused by the shock wave itself. Detonation typically damages the piston edges (I recall learning this but I don't recall the exact process). Personally, I don't buy Jeep's claim that light pinging is harmless and so I run 91 (highest we can readily get here), and the pinging is gone. The engine also doesn't have surges in the power delivery as the engine management tries to compensate for the pinging.

 

[guarnibl]

May the force be with you.

 

[Hound Dog]

Quit buying gas at the discount hajimart that sells a tank a month and go to a busy station with fresh gas. Report back after running a few full tanks.

 

[Petey]

@Petey

Why did you decide to run an octane booster instead of buying mid grade or premium? The owner's manual specifically says not to run octane boosters FYI, the dealership could give you grief and blame it for causing your preiginiton occurrences.

I still can't get over them saying that there is no benefit on these engines to running premium, but then the very next sentence they say you may experience audible knock while running 87 but that it's cool. You know what resists knock? Higher octane gas, sounds like a benefit to me. Call me old fashioned but I like my air fuel mixture to combust correctly, not erratically. The more the engine senses preigniton, the higher knock control will rise and the ECU will revert to a less aggressive fuel table for the same conditions accordingly. Saying otherwise is misleading.

I agree ..but I do believe Lucas fuel treatment doesn't have the methanol smell like the octane boosters do but I could be wrong... . I tried checking, and so far, nothing to substantiate that ingredient. Also, i'm mindful that it could mess with the converter however, the car has run so much smoother with it that , I don't think I'll be going back . I also find it ridiculous how 87 octane is what the engine supposed to run on yet for many of us , thats absolutely not true. So in the end how can one trust jeeps recommendations when they themselves state 87 may cause pinging but u should use it anyway. They are contradicting themselves and one can only see it this way. Jeep expects the engine to last the few miles that way under warranty , but after that ur stuck with whatever damage has incurred . I t's very clear they came across preignition problems when designing the engine just from the wording on that paragraph . I'm going to carry my snake oil bottle with me for every fill up. Gas is like a box of chocolates.

 

[DanW]

I agree ..but I do believe Lucas fuel treatment doesn't have the methanol smell like the octane boosters do but I could be wrong... . I tried checking, and so far, nothing to substantiate that ingredient. Also, i'm mindful that it could mess with the converter however, the car has run so much smoother with it that , I don't think I'll be going back . I also find it ridiculous how 87 octane is what the engine supposed to run on yet for many of us , thats absolutely not true. So in the end how can one trust jeeps recommendations when they themselves state 87 may cause pinging but u should use it anyway. They are contradicting themselves and one can only see it this way. Jeep expects the engine to last the few miles that way under warranty , but after that ur stuck with whatever damage has incurred . I t's very clear they came across preignition problems when designing the engine just from the wording on that paragraph . I'm going to carry my snake oil bottle with me for every fill up. Gas is like a box of chocolates.

Lucas has a few good products but some of them are just garbage. For example, their oil treatment is basically a heavy oil, as in a 50 weight, IIRC, with few or no additives. Ridiculous. One of my friends swears by that crap and runs one quart of it with 5 quarts of 5w20 every time he changes oil in his 2013 Pentastar. So basically he turns it into a 10w30 or so, but with a lower percentage of important additives. One thing I've told him he's likely to do is mess up his cat converters. Fortunately, the Pentastar seems to handle it. He refuses to believe that it is just heavy oil, even though folks on Bitog have sent it to Blackstone and proven it to be just that.

I wouldn't run anything Lucas unless I knew exactly what was in it. I do believe they make a good firearm lube, though. But that is easy compared to more complicated automotive products.

 

[Petey]

Quit buying gas at the discount hajimart that sells a tank a month and go to a busy station with fresh gas. Report back after running a few full tanks.
[/QUOTE
The BP I usually buy from is on a main road with a lot of traffic going trough . I bought fuel from many makers ...was just the same. My next tankfull I'll be putting 90 plus to see what happens. But I can pretty much predict the outcome.. that it will be same as the treatment. I never seen this hajimart ..must have terrible gas .

 

[Petey]

Lucas has a few good products but some of them are just garbage. For example, their oil treatment is basically a heavy oil, as in a 50 weight, IIRC, with few or no additives. Ridiculous. One of my friends swears by that crap and runs one quart of it with 5 quarts of 5w20 every time he changes oil in his 2013 Pentastar. So basically he turns it into a 10w30 or so, but with a lower percentage of important additives. One thing I've told him he's likely to do is mess up his cat converters. Fortunately, the Pentastar seems to handle it. He refuses to believe that it is just heavy oil, even though folks on Bitog have sent it to Blackstone and proven it to be just that.

I wouldn't run anything Lucas unless I knew exactly what was in it. I do believe they make a good firearm lube, though. But that is easy compared to more complicated automotive products.

The only product from lucas I use is the fuel additive .. and have done for decades on a few vehicles. Actually, I don't use anything else... any additives anywhere else on any car ..they get straight everything. I don't claim to know every thing but I had only good results with it ....never a negative. ...If u let the tank full sit a long time this helps to keep the fuel from going stale so quickly. One thing I don't get is how the heavy oil should affect the cat so directly unless he's pushing it through the exhaust . If he is and no problems I should be ok with mine.

 

[m3reno]

Adding octane boosters only raises your octane a few points meaning if you get 87 octane at the pump and add octane boosters, the amount of points (generally 2) they are referring too would increase your octane to 87.2 not 89. you would need 5 bottles for it to increase a full point.

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