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Old 02-29-2012, 10:21 PM   #1
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89 or 93 octane?

what should be better to run with 89 or higher octane? I'm not goin to do a lot of off road activities. anyone can help me on these? thanks guys.

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Old 02-29-2012, 10:22 PM   #2
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Which ever is cheapest.

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Old 02-29-2012, 10:24 PM   #3
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89
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Old 02-29-2012, 10:26 PM   #4
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Your owner's manual tells you exactly. 89 octane for me (usually most jeeps), cheapest and I know my rig was meant to use it.
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Old 02-29-2012, 10:28 PM   #5
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I've always used 87. I am pretty sure that is what the manual says to use.
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Old 02-29-2012, 10:35 PM   #6
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ok yeah the manual said 89. i was asking since on my other trucks i had before i used to run it with 93 so i can get the engine more clean n valves as well so i was thinking that i could do the same on my new baby boy! lol have anyone run 93?
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Old 02-29-2012, 10:36 PM   #7
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the octane rating is nothing more than resistance to detonation. That is all. Unless you've done something specific to change the effective compression ratio, there is absolutely no reason to run anything other than what the manual states.
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Old 02-29-2012, 10:44 PM   #8
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what should be better to run with 89 or higher octane? I'm not goin to do a lot of off road activities. anyone can help me on these? thanks guys.
It's better to avoid running anything higher than the 87 octane your engine was designed for. Really.

Octane's purpose is not more power or better engine cleaning. Octane's sole purpose is to reduce how easily the gasoline ignites from being compressed. Simply put, octane is added to help gasoline resist igniting from being compressed too much. It also slightly slows how fast the gasoline burns.

More octane is added/needed when an engine is designed with higher than normal compression levels. Extra octane is added so the gasoline doesn't self-ignite and start detonating prematurely which causes pinging and knock when the engine's compression level is purposely designed to be higher than normal. Higher octane levels are only needed in "high-compression" engine. The higher power levels from high compression engines come from the high compression levels... not from the higher octane fuels required whch serve only to prevent pinging and premature gasoline detonation from the extra-high compression level.

89, 91, and 93 octane gasolines contain no more power or cleaning additives than 87 does either.

In fact, running a higher octane than an engine was designed for can actually cause engine deposits to form due to the higher octane fuel being harder to ignite and slower to burn.

Your engine will run just as well with 87 than it would with a higher octane. And it can actually run better long-term due to reduced deposits if you avoid using higher octane fuels than it was designed for.

None of our Wrangler engines were designed for any octane higher than 87. There are no benefits to running higher than 87 in our Jeep engines and in reality, there are only drawbacks in the long run.

So no, you won't gain anything by running a higher octane gasoline. Not more power, not better fuel economy, and certainly not a cleaner engine or cleaner fuel injectors. Run 87 and not only will you save $$$, your engine will actually perform better with 87.

Edit: U.S. octanes are calculated differently than in other countries. Are you perhaps not in the U.S.? If so, your 89 octane rating may equal a U.S. 87 octane.
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Old 02-29-2012, 10:48 PM   #9
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^ +2
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Old 02-29-2012, 10:58 PM   #10
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Old 02-29-2012, 11:02 PM   #11
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Wow thanks so.much for so much info now I know I need to.run on 89 I was so confuse about it! Again thanks so much.
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Old 02-29-2012, 11:04 PM   #12
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Wow thanks so.much for so much info now I know I need to.run on 89 I was so confuse about it! Again thanks so much.


Your engine runs best on 87 octane
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Old 02-29-2012, 11:06 PM   #13
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Wow thanks so.much for so much info now I know I need to.run on 89 I was so confuse about it! Again thanks so much.
If you're in the U.S. you should run 87, not 89.
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Old 03-01-2012, 12:17 AM   #14
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Basically to add to what Jerry said or maybe just another angle on it...since our oem Wrangler motors are designed for 87, if we run 89, 93 or Race Fuels in our motors those higher octanes have a higher flashpoint and you will actually lose some power. 87 will create the most power for our motors.
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Old 03-01-2012, 12:53 AM   #15
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I have an '03 Rubicon and there is no way my JEEP will run on anything lower than 91 octane. If I run the 87 it will ping pretty bad under load.
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Old 03-01-2012, 01:07 AM   #16
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Then there is something wrong with your Engine.. The 4.0 was designed to run best on 87 octane.. Im not sure what is wrong with your engine but something is
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Old 03-01-2012, 04:04 AM   #17
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If you have problems running on anything but high octane, you may have a large amount of crap in the cylinders causing the displacement to shrink and compression to increase. You should use some kind of product like seafoam or another combustion chamber cleaner to clear out the engine.
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Old 03-01-2012, 05:16 AM   #18
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Old 03-01-2012, 05:27 AM   #19
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My Jeep ate cats when I put premium in the tank......now only run 87..your money your Jeep.
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Old 03-01-2012, 11:22 AM   #20
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If you have problems running on anything but high octane, you may have a large amount of crap in the cylinders causing the displacement to shrink and compression to increase. You should use some kind of product like seafoam or another combustion chamber cleaner to clear out the engine.
Could also be an ignition timing issue. Too much advance will cause ping (aka "knock") on most motors...

But I'm a jeep NOOB, so I'm not sure how the ECU handles ignition timing yet. Do our jeeps even have a knock sensor?
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Old 03-01-2012, 11:31 AM   #21
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Off topic, but I wish I could get 93 in California(from a gas station). My Camaro runs so much better on it.
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Old 03-01-2012, 11:32 AM   #22
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I run the cheapest, thats what jeeps r made for.
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Old 03-01-2012, 01:05 PM   #23
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Amoco and Shell run 5x the detergents in their premiums...
That is the only reason to consider using it....
The octane is not needed.
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Old 03-01-2012, 01:08 PM   #24
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Amoco and Shell run 5x the detergents in their premiums...
That is the only reason to consider using it....
The octane is not needed.
What is your proof of that?
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Old 03-01-2012, 04:42 PM   #25
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If you have problems running on anything but high octane, you may have a large amount of crap in the cylinders causing the displacement to shrink and compression to increase. You should use some kind of product like seafoam or another combustion chamber cleaner to clear out the engine.
my dads f-150 v6 does exactly this. when new it thrived on 87 but due to very poor maintenance and lack of care it now runs best on a minimum of 89 octane.

Its a good idea to run a fuel system cleaner (preferably a strong one that contains P.E.A. like Mopar's Combustion Chamber Cleaner ) at the end of every oil change. Those stronger fuel system cleaners will usually say to use no more then every 3k miles. I would also do a good thorough Italian tuneup while using the cleaner

or you can maintain a clean combustion chamber by using a mild cleaner in every tank (Like marvel mystery oil) and doing a Italian Tune up every now and then.

If your wondering, an Italian up is giving the engine wide open throttle runs going to high RPM then letting the engine rev back down. doing this several times. The engine needs to have load and be fully warmed up when doing this. if you have an automatic place the shifter in 2nd and if you have a stick try it in 3rd (i dont have a stick so im unsure of what speeds each gear is) and start out at a slow speed (or stop if your in the automatic) and floor it until your engine reaches 4-5k RPM (jeep recommends revving above 3200 RPM to rotate the valves to keep deposits from sticking to the valve seating area, so your killing 2 birds with 1 stone). Then let the engine slow itself down by engine breaking, dont use the breaks and dont shift to the next gear. the repeat a few times. Of course only do this in a safe place with no traffic.

doing these should keep carbon from building up in your engines cumbustion chambers.
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Old 03-01-2012, 05:02 PM   #26
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It's real simple. Use what the manual says!

Running too much octane does nothing and only creates problems. Unless you have knock, then increase it but that is just a bandaid. You have deposits as previously mentioned.

Some cars that recommend higher octane can still run on lower if they have knock sensors, you just might loose a few hp.
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Old 03-01-2012, 05:44 PM   #27
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Doesn't matter what you drive, unless you have changed your compression ratio by adding a power adder, changing the size of your combustio chamber, or advancing your timing, you should only use the octane called for for your vehicle. Its just a waste of money.
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Old 03-01-2012, 07:26 PM   #28
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For those whose engines ping unless they run a higher than 87 octane...

Pinging is caused by the fuel igniting premaurely. More serious pinging, aka knock aka pre-detonation, is a serious issue that can cause engine damage.

What is the typical/most common cause of an engine pinging when the correct octane grade is used? The most common reason is the gasoline is being compressed excessively. Similar to how diesel is ignited by nothing more than a high amount of compression. Using a higher-octane gasoline combats that by helping the gasoline to resist being detonated by excessive compression. But that is just a band-aid fix which is not treating the root cause of the pinging.

What is the most common reason for the excessive compression that causes the pinging? Carbon build-up inside the combustion chambers. The more carbon inside the combustion chamber, the more volume the carbon takes up inside the combustion chamber. That raises the pressure inside the combustion chamber, much like shaving the head does or other techniques for reducing the volume inside the combustion chamber which increases its pressure during the combustion stroke. That is the most common cause of pinging... from the gasoline being overcompressed which causes it to self-detonate... again, like how diesel ignites on its own from nothing more than being compressed enough.

What usually or at least often causes excessive carbon inside the combustion chamber? Driving the engine too conservatively. Never revving it hard enough, or not revving it hard enough regularly enough. Engines need to be pushed hard once in a while to keep the carbon blown out and the combustion chambers clean. People who drive like the proverbial little old lady, often thinking they are helping their engines last longer, are the ones most likely to develop carbon inside the combustion chambers... which then causes pinging, which then causes the owner to have to start running a higher octane gasoline to stop or limit the pinging

How to get rid of the carbon? The easiest is to perform what some call a "Polish Tuneup" which is nothing more than driving super-aggressively for a few days, revving the engine hard to high, close to redline, RPMs. Repeatedly. Mechanics for automotive dealerships that work on high performance cars like Corvettes have to do something like that all the time. Many of their customers don't drive their vehicles aggressively enough which causes the carbon build-up. So they come in complaining how their high performance car is running like crap. In response, the mechanic will either blow the carbon out in the back lot by repeatedly revving the engine hard by hand, or take it out to the nearest deserted road and drive it hard until the carbon is blown out. After that is done, the engine is normally fine again.

Or you can use the 'Water Technique' I've talked about here (use the Search function) which is perhaps the most effective technique for cleaning out carbon deposits.

So if your engine is pinging, odds are very good it's caused by nothing more than excessive carbon buildup inside the combustion chamber. Running a higher octane gasoline is strictly a band-aid fix that is treating the symptom, not the root cause. Stop pussy-footing it.
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Old 03-01-2012, 08:41 PM   #29
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Lol, next time I get pulled over I am telling the officer that I am cleaning my engine! With my driving habits, my engines must be spotless.
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Old 03-01-2012, 08:48 PM   #30
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idk about you but when i hammer down the throttle, get the engine screaming, jeep rattling and top flapping violently in the wind,feel adrenaline pump threw my veins as i struggle to keep the jeep on the road i often look down to see im only going 55MPH.

its a jeep thing!

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