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      11-28-2012, 04:52 PM   #1
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89 Octane performance IMO

Ive been getting 89 Octane a lot lately just to compare it to 93 octane and it seems like it really affects performance. Maybe its in my head, but it feels very sluggish running at 89 octane. Anyone else experience the same?
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      11-28-2012, 04:57 PM   #2
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Originally Posted by jzcrna View Post
Ive been getting 89 Octane a lot lately just to compare it to 93 octane and it seems like it really affects performance. Maybe its in my head, but it feels very sluggish running at 89 octane. Anyone else experience the same?
i am running on 91 and honestly i can't notice any difference vs 93, and also it costs the same
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      11-28-2012, 05:07 PM   #3
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Originally Posted by jzcrna View Post
Ive been getting 89 Octane a lot lately just to compare it to 93 octane and it seems like it really affects performance. Maybe its in my head, but it feels very sluggish running at 89 octane. Anyone else experience the same?
Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power. I highly suggest not running 89 in a turbo car, you can lean the car out causing detention, especially in the high RPM's. It's very bad for the engine.
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      11-28-2012, 05:19 PM   #4
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Originally Posted by EB_F30 View Post
Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power. I highly suggest not running 89 in a turbo car, you can lean the car out causing detention, especially in the high RPM's. It's very bad for the engine.
what are you using, and what you think about 91?
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      11-28-2012, 05:24 PM   #5
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Originally Posted by EB_F30 View Post
Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power. I highly suggest not running 89 in a turbo car, you can lean the car out causing detention, especially in the high RPM's. It's very bad for the engine.
Lower octane rating means it's more susceptible to detonation, which can cause the computer to retard the timing. That's where power reduction comes from.
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      11-28-2012, 05:31 PM   #6
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Originally Posted by S-Dot
Quote:
Originally Posted by EB_F30 View Post
Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power. I highly suggest not running 89 in a turbo car, you can lean the car out causing detention, especially in the high RPM's. It's very bad for the engine.
Lower octane rating means it's more susceptible to detonation, which can cause the computer to retard the timing. That's where power reduction comes from.
Thanks, there's not much a cost difference to have a more enjoyable driving experience as well.
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      11-28-2012, 05:35 PM   #7
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Lower octane rating means it's more susceptible to detonation, which can cause the computer to retard the timing. That's where power reduction comes from.
^ This . IF your car calls for premium then you should use it.As S-Dot said you'll get detonation,causing the timing to retard
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      11-28-2012, 05:41 PM   #8
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Quote:
Originally Posted by EB_F30 View Post
Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power.
Higher octane fuels does not contain more energy nor does it require more oxygen for combustion. It merely contains additives that make it less likely to self-detonate.

The only time the use of higher octane fuel results in more power is when an engine is specifically designed for higher octane and, then, only in comparison to when improperly low octane fuel is used in this same engine. As already pointed out above, the use of lower octane in such an engine will pull the timing under some circumstances, reducing power.

The F30 is perfectly happy with 89 octane, as called out in the manual and on the fuel filler door. Some claim 91 produces more power. BMW indicates its power output numbers were produced running 91, but does not state the engines produce more power with 91 nor state that 89 produces less power.

As a practical matter, there will be only a small difference - ~ 3% - if the engine retards the timing on lower octane. This is a difference difficult to detect with a butt dyno.
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      11-28-2012, 06:02 PM   #9
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Originally Posted by EB_F30 View Post
Less octane in the fuel is not going to burn as well...more octane equals more power because the fuel is more potent and it's also burning more air...thus making more power. I highly suggest not running 89 in a turbo car, you can lean the car out causing detention, especially in the high RPM's. It's very bad for the engine.
Dude, so many errors in one post.......good job
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      11-28-2012, 07:37 PM   #10
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Dude, so many errors in one post.......good job
Points for confidence though
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      11-28-2012, 08:57 PM   #11
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Turbo cars especially need higher octane or high compression engines.... with all that compressed air in the combustion chamber you want to make sure that the fuel gets ignited when its supposed to get ignited. Not when its not supposed to, which in that case you will get detonation. Low octane means that the fuel is less stable compared to high octane. Low octane will pre-ignite from the heat generated from the cylinder walls. Compressed air, fuel and heat you will get a boom when fuel can be easily ignited!

Its like diesels... there is no spark plug... just compressed air, diesel and you get BOOM!
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      11-28-2012, 09:44 PM   #12
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the manual actually specifies that 89 is useable in the 328i as well as the 335i. 5 octane points is actually quite dramatic when it comes to power. you should look at the cars dynoing on on 91 and 93 with comparable mods. it can sometime show a pretty decent disparity.
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      11-28-2012, 10:24 PM   #13
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Originally Posted by TreDirtyFive View Post
the manual actually specifies that 89 is useable in the 328i as well as the 335i. 5 octane points is actually quite dramatic when it comes to power. you should look at the cars dynoing on on 91 and 93 with comparable mods. it can sometime show a pretty decent disparity.
Only if the car is tuned to be affected by higher octane. We have no indication that putting 93 in our cars will give more power. I run it because I cant find 91, but I dont even notice a difference between 89 and 93. I'm just assuming that it will slightly pull timing if it senses 89, but my butt dyno couldn't tell. In fact I felt like the car had more power when I ran 89, but that's probably because that was my first two tanks and it seemed like a rocket compared to my 4x4 f150 lol
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      11-28-2012, 11:14 PM   #14
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In all honesty, I tried 89 and then went with 94. I don't know why but I clearly feel a difference in mileage and power in my 335i after using 94 quite a bit.

Hence I continue using 94 and very happy with it. It's only costing me a few more dollars but I'm happy with the outcome...
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      11-29-2012, 12:39 AM   #15
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Quote:
Originally Posted by ZmmF30xi
Turbo cars especially need higher octane or high compression engines.... with all that compressed air in the combustion chamber you want to make sure that the fuel gets ignited when its supposed to get ignited. Not when its not supposed to, which in that case you will get detonation. Low octane means that the fuel is less stable compared to high octane. Low octane will pre-ignite from the heat generated from the cylinder walls. Compressed air, fuel and heat you will get a boom when fuel can be easily ignited!

Its like diesels... there is no spark plug... just compressed air, diesel and you get BOOM!
Higher octane. Not higher compression. Look at any naturally aspirated car with turbo kits. You want to lower compression for more power and safety. No? Or at least thats how it was back in the day. Either that or have really low boost.
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      11-29-2012, 06:46 AM   #16
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Just curious and not meaning to hi-jack, but anyone have any idea what they generally have available for fuel octane in Europe.? I have always run premium in all cars (94 when I could get it). I would like to know what is generally available elsewhere as they are getting the same engine. I mean BMW "recommends" BP gas in the manual, but I have only seen one station thst I can think of, LOL!
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      11-29-2012, 08:10 AM   #17
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Without breaking out the wiki,

Gasoline is a distilled fuel from hydrocarbons. There are a number of different compounds in the family of hydrocarbons. Any of these fuels will ignite with the right pressure/heat. High-octane fuel contains a higher percentage of these that are resistant to combustion at higher pressures. This will become important in a moment.

Remember that the fuel needs to be able to withstand the increasing pressure in the chamber as the piston travels upward and compresses the mixture. If it detonates early, then you don't get the full power stroke, because the piston is stil on the upstroke when the ignition occurs.

For most car engines, this high grade of fuel isn't necessary. The compression ratio is relativally mild, and so there's no danger of premature detonation; the piston will travel the full distance and the fuel will only ignite with the spark plug. In a high performance engine like the N55, the compression ratio is high, and the engine compresses the mixture higher to extract more energy. Because higher compression ratios are used, the grade of fuel needs to be high to allow for the engine to compress it further, and only detonate with sparked...drawing maximium power out of the stroke for which the engine was designed. Using lower grade fuel results in the scenario as stated above. Modern engines will compensate with their sensors and computer control, and so adjust the timing such that the sparks occur earlier, resulting in the power loss as others described earlier.

So, to recap: Higher octane fuel means it can withstand higher pressures. Same energy amount. For economy engines, it has no effect. On a performance car, it determines whether or not you obtain all of the power for which the engine was designed.

In any case, without going back to the book, I believe that's the rough idea. Hope this helps; my apoligies for reiterating some facts others posted before me. =)

Last edited by Kozality; 11-29-2012 at 08:12 AM. Reason: Removed pkim1079's quote, I misread his post.
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      11-29-2012, 10:06 AM   #18
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If you buy a $40-50k car and can't afford the extra $.20 per gallon you should have reconsidered your purchase.

Aside from the knock sensor killing the engines power, you'll most likely notice you're losing fuel economy as well. I did this as a test on my Acura (which was tuned for 91) and noticed I consistently got 2-3mpg less when driving with 87, aside from the power difference. Which basically translates to the 10% worse fuel economy negated the 5% I was saving per gallon.
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      11-29-2012, 10:55 AM   #19
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The manual says that 89 octane (not 91 or 93) is the required fuel. So I'm sure the engine is tuned for 89 octane, unless BMW made an error in the manual and on the fuel filler door.
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      11-29-2012, 11:33 AM   #20
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After three days of 89 octane my has mileage is obviously worse than it was. No question.
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      11-29-2012, 11:56 AM   #21
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Quote:
Originally Posted by tdizzle View Post
Points for confidence though
haha...I'll take it! I stand corrected though. I actually thought the higher the octane the more potent the fuel was enabling more timing etc but its that it actually burns slower you can increase timing etc giving you more power. I don't have my car yet but I am actually surprised to see it doesn't require a higher octane fuel. Good stuff....
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      11-29-2012, 08:08 PM   #22
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The manual says that 89 octane (not 91 or 93) is the required fuel. So I'm sure the engine is tuned for 89 octane, unless BMW made an error in the manual and on the fuel filler door.
Yes.

Many want to believe the car is made for/requires/runs better on higher octane, thinking it is a badge of superiority. Remember however, one can get just as drunk on beer as champagne.

Fortunately, even if an engine is designed for high octane fuels, the performance hit is minor - well below that we will ever be able to detect as drivers.

For example:

"The Genesis Coupe 3.8 Track comes with Hyundai's updated-for-2013 3.8-liter V6 which is now good for 348 hp and 295 lb-ft of torque on 91-octane fuel. Power and torque are diminished by 4 hp and 3 lb-ft on 87 octane fuel." See, clicky

You are never going to feel the difference between 348 bhp and 344 bhp.
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