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Old 12-31-2012, 08:55 AM   #1
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93 vs 87 (Octane)

I feel like some of you might get mad at this post for some reason...it seems anti jeep. Anyways this is my first jeep after owning 3 BMW's so I'm used to putting in 93 octane. I started off by putting in 87 but then prices dropped below $4.00 for 93 and I figured why not.. Not kidding....it runs so much better. Now thats all I put in. I also feel like a tank of 93 last longer....but I don't know if I wanna go on record with that one.. Anyone else run 93??

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Old 12-31-2012, 09:02 AM   #2
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You thinking it runs better is in your head and yes these threads are hates because:

1.) this topic has been beaten to death
2.) using higher octane is proven to not have benefits in a NA vehicle and if anything will lean towards the side of being detrimental.

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Old 12-31-2012, 09:02 AM   #3
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I've heard this argument a lot. Jeep recommends standard gas be it 87 or 85 whatever low octane is in your area. But whatever works for you. I run the rec octane and pull 22mpg highway driving
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Old 12-31-2012, 09:03 AM   #4
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After using 93 in the mini for so long, I will say it was awesome selecting 87 again this weekend! I admit putting a higher grade in a car isn't that big of a deal from a cost perspective, but it sure makes a physiological difference! I always just go with the manufactures recommendation since that is how the car was designed to run.
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Old 12-31-2012, 09:14 AM   #5
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BMW..... What kind of lift kit?
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Old 12-31-2012, 09:19 AM   #6
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Running 93 octane in an engine designed to run 87 is the equivalent of retarding the timing. It's harder to ignite and allows you to run more timing IF your vehicle is tuned for it. Some vehicles can detect the octane and adjust the timing as needed but our tune of the 3.6 does not.
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Old 12-31-2012, 09:19 AM   #7
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Quote:
Originally Posted by xcoaste View Post
After using 93 in the mini for so long, I will say it was awesome selecting 87 again this weekend!
I'm with you there. My last car was a Saab turbo (premium gas required). So while I've been using 93 for the last five years, I'm happy to once again use 87.
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Old 12-31-2012, 09:50 AM   #8
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Running a higher than the factory recommended octane does absolutely no good except maybe for the placebo effect. One exception, if you've done some extensive engine mods and boosted the compression ratio or changed the timing, THEN you might benefit from it.

On my old car that uses 87 octane I experimented with 87, 89 and 93 for a month each. The 87 and 89 octanes were so close in the mpg that it was insignificant. However, on the 93 my mpg actually DROPPED by 2 mpg. I use whatever is recommended in the owners manual in all my vehicles.
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Old 12-31-2012, 09:57 AM   #9
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I used to think old school and run premium in vehicles that didn't require it, but that was prior to more sophisticated computer controlled engines. Now I stick with what is indicated in the manual which is 87 octane. My 10 Rubi runs great on it. It seems to like Shell best for some reason; probably I seem to like Shell best rather than the Rubi. I was used to putting in 93 in an M3. It took a little while but I broke the high octane fix.
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Old 12-31-2012, 10:03 AM   #10
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Ok....thanks for the posts. Switching to 87...
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Old 12-31-2012, 10:25 AM   #11
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94 yj 2.5 33's. I run 87 most of the time. On the highway I can go 55 up most hills before I have to downshift to 4th. If I run 93 I can do 70 comfortably. That being said I do not run 93 all the time. Probably once every 5th or 6th tank.
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Old 12-31-2012, 12:15 PM   #12
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The last rig I could actually measure any performance difference in high/low octane, was my 1973 Chev 454 Camper Special pick up.

With 87 would average 10 mpg running or standing still, loaded or empty bed.

Running 92+ proof it would get nearly 13 under the same conditions.

When towing over mountains I'd use high octane, while running in the flat country didn't seem to matter much....but it was an old style carb model with absolutely zero computer anything.

I've tried extensive tests in my 08JK for high/low/non ethanol varieties of the juice. 87 works as good as any of them, under any conditions I've tested.
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Old 12-31-2012, 04:56 PM   #13
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Quote:
Originally Posted by kyvtx1300
BMW..... What kind of lift kit?
Ahahaha
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Old 12-31-2012, 05:02 PM   #14
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My TJ ate catalytic converters when I ran premium...once I went back to regular problem stopped.....that is what is recommended and also for the JK so that is what it gets.
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Old 12-31-2012, 06:46 PM   #15
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Quote:
Originally Posted by sinepome View Post
94 yj 2.5 33's. I run 87 most of the time. On the highway I can go 55 up most hills before I have to downshift to 4th. If I run 93 I can do 70 comfortably. That being said I do not run 93 all the time. Probably once every 5th or 6th tank.
Unless you've dramatically modified that little 4-banger, you're imagining things.

Once again ........ running anything more than 87 octane on your STOCK JEEP engine will NOT create any more power nor add any benefits.

This is NOT an opinion. It's a FACT. If you doubt this, research the benefits (or lack thereof) of octane and see for yourself.

In your defense, the ONLY thing that may be helping your performance is the lack of ethanol blended in some higher octane premium fuels. If that is the case, then your performance differences may be real. But it is NOT the OCTANE level, it is the lack of ethanol in the 93 octane that you are using. You may also see some minor improvement in performance by using 87 octane fuel that is NOT an ethanol blend. These fuels are still available in some areas of the country if you seek them out.

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Originally Posted by JeeperJake View Post
The last rig I could actually measure any performance difference in high/low octane, was my 1973 Chev 454 Camper Special pick up.

With 87 would average 10 mpg running or standing still, loaded or empty bed.

Running 92+ proof it would get nearly 13 under the same conditions.
ABSOLUTELY. The older '70s vintage 454s and other high-performance motors were higher compression engines that ran optimum ignition timing and could actually utilize the higher octane. Unfortunately, those are few and far between in today's production cars.
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Old 01-01-2013, 11:17 AM   #16
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Quote:
Originally Posted by Steve305

Unless you've dramatically modified that little 4-banger, you're imagining things.

Once again ........ running anything more than 87 octane on your STOCK JEEP engine will NOT create any more power nor add any benefits

.
I'm not sure if my imagination is strong enough to pull my jeep up a hill without me downshifting. My engine is bored over to maybe a 2.6 but that's pretty much only modifications done. There was enough of a difference in power that my girlfriend asked if I had done something to the jeep. It's a pretty common joke around our house that the jeep "doesn't go over 65 downhill". I'm not trying to get into an argument but I knows what I knows. Someone said earlier that the higher octane can retard timin,g and this could cause the effect I'm talking about. On a different note, In my 89 Honda I did get worse gas mileage with 93 over 87.
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Old 01-01-2013, 11:52 AM   #17
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Originally Posted by sinepome View Post
I'm not trying to get into an argument but I knows what I knows. Someone said earlier that the higher octane can retard timin,g and this could cause the effect I'm talking about. On a different note, In my 89 Honda I did get worse gas mileage with 93 over 87.
You might "know what you know", and that's OK. But to argue with basic scientific facts and proven technology doesn't gain you any respect.

Also, WHERE did you read on here that "higher octane can retard timing"? Timing is controlled by the ignition system ... octane has nothing to do with timing settings.

Obviously (by your "timing" remarks) you have very little knowledge of combustion engine basic operations. If you spend a little time doing the proper research you will understand why your observation about the gains you proposed is highly questionable. We all had to learn sometime, and none of us were born with mechanical skills or systems knowledge. Do some research.
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Old 01-01-2013, 12:08 PM   #18
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Quote:
Originally Posted by Steve305

You might "know what you know", and that's OK. But to argue with basic scientific facts and proven technology doesn't gain you any respect.

Also, WHERE did you read on here that "higher octane can retard timing"? Timing is controlled by the ignition system ... octane has nothing to do with timing settings.

Obviously (by your "timing" remarks) you have very little knowledge of combustion engine basic operations. If you spend a little time doing the proper research you will understand why your observation about the gains you proposed is highly questionable. We all had to learn sometime, and none of us were born with mechanical skills or systems knowledge. Do some research.
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Originally Posted by ranjr
Running 93 octane in an engine designed to run 87 is the equivalent of retarding the timing. It's harder to ignite and allows you to run more timing IF your vehicle is tuned for it.
I'm not trying to argue with anything scientific or not. Nor am I trying to gain respect from anyone on the inter-webs. If I were, I would be making build threads and flexing my mechanical nuts all over the place. I was simply stating an observation. You get all bent out of shape about it because it doesn't go along with your position. You attacking my "knowledge of combustion engine basic operations" to hurt my feelings?as I stated before. I don't care what anyone thinks I can or can't do.
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Old 01-01-2013, 01:25 PM   #19
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Anyone that understands the difference between 87 & 93 octane should know that 93 is harder to ignite during the combustion process. Since it takes longer to ignite, it's essentially retarding the timing. The computer is still lighting the spark plug at the same time, but the fuel doesn't ignite as quickly.
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Old 01-01-2013, 01:30 PM   #20
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Mine runs best on Chevron 87
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Old 01-01-2013, 01:48 PM   #21
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I don't think higher octane it is harder or takes longer to ignite, but with higher compression ratios the lower octane fuel can ignite before the spark due to heat and compression of the air fuel mixture. The way a diesel engine works (no spark plugs). That would cause a decrease in performance of a high compression motor i.e. a turbo charged 4 banger. So I would imagine no performance, or gas mileage increase for a standard engine using high octane fuel. It just cost more to fill up.
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Old 01-01-2013, 03:12 PM   #22
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Originally Posted by sinepome View Post
I'm not trying to argue with anything scientific or not. Nor am I trying to gain respect from anyone on the inter-webs. If I were, I would be making build threads and flexing my mechanical nuts all over the place. I was simply stating an observation. You get all bent out of shape about it because it doesn't go along with your position. You attacking my "knowledge of combustion engine basic operations" to hurt my feelings?as I stated before. I don't care what anyone thinks I can or can't do.
Forgive my "attacking". I wasn't trying to hurt any feelings. Forgive me if I sounded like that. But the bottom line is that running higher octane fuel in your stock 2.5 or 4.0 will NOT result in an increase in performance. It's just a plain and simple fact. It's been proven time and time again by people that are way smarter than me or you. Industry experts have researched this in real-life situations and laboratories for years with the same results. If you saw some type of performance increase on any given day, it was something other than an octane change. It's not my opinion or "position". It's just the plain 'ole truth.

Quote:
Originally Posted by ranjr View Post
Anyone that understands the difference between 87 & 93 octane should know that 93 is harder to ignite during the combustion process. Since it takes longer to ignite, it's essentially retarding the timing. The computer is still lighting the spark plug at the same time, but the fuel doesn't ignite as quickly.
Not sure I would consider that a timing retardation, but more a case of "incomplete combustion" since the piston is usually past the power stroke and advanced to the exhaust stroke by the time the higher octane mixture completes the burn die to lack of compression. But regardless of what we call it ... we both agree that it's definitely NOT an advantage and incapable of gaining performance in our stock Jeep motors.
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Old 01-06-2013, 12:53 PM   #23
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Our jeeps are designed to run on 87 octane!
Higher octane will be a total waste of money with no additional benefit!
If you have some extra money that you want to spend, then please, send it my way and I will find a good use for it...........
Don't let anybody tell you that with higher octane you will have more power, or get better mileage, because it will not happen.

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