Engine/Power - EJ25T (STI and 2006+ WRX) Discussions about the USDM 2006+ WRX and WRX STi 2.5 liter turbo flat-four.

fuel octane question

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Old Sep 12, 2011 | 10:41 AM
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fuel octane question

Will it affect my car's performance or engine if I used 87 octane instead of 91?
Old Sep 12, 2011 | 10:45 AM
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YES! the car needs 93 but we dont have that in Cali. If its cause gas cost alot the difference in price in filling up with 91 and 87 is about $2.60 a fill up and that a lot less then a new engine.
Old Sep 12, 2011 | 11:20 AM
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Originally Posted by subie07
Will it affect my car's performance or engine if I used 87 octane instead of 91?
Octane is the resistence to engine knock & the way it burns so you'll def **** up your engine dude, plus your car will lower peak boost, making it run like ****. Don't do it, it'll do more harm than anything, put 91 or higher OCT only, nothing less. Turbo cars nowadays always need higher octane, you should know that, this shouldn't even be a question dude!
Old Sep 12, 2011 | 04:41 PM
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As others have already said, there's a reason why the higher octane is required.

Engine knocking - Wikipedia, the free encyclopedia

Severe knocking can lead to catastrophic failure in the form of physical holes punched through the piston or cylinder head (i.e., rupture of the combustion chamber), either of which depressurizes the affected cylinder and introduces large metal fragments, fuel, and combustion products into the oil system.
Old Sep 12, 2011 | 04:46 PM
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I was hoping this thread was going to be about using a higher than 91 octane on a stock tune or on an OTS map tuned car.
Old Sep 12, 2011 | 08:48 PM
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[QUOTE=STiWRX06;3131964]Octane is the resistence to engine knock & the way it burns so you'll def **** up your engine dude, plus your car will lower peak boost, making it run like ****. Don't do it, it'll do more harm than anything, put 91 or higher OCT only, nothing less. Turbo cars nowadays always need higher octane, you should know that, this shouldn't even be a question dude![/QUOT

Well like my father always used to tell me..."its better to ask a thousand stupid questions, than make one big mistake". So it might have been a silly question, but thats why I asked. I figured you guys would know more
Old Sep 13, 2011 | 12:11 AM
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All good man, just don't run 87 or even 89, only 91 comprende. Just looking out for ya man, there's a reason it tells you only high octane fuel in the owner's manual & that bigass decal right inside the fuel door, no deviations, unless you can find some 93 (what are cars are intended to use in the first place for max reliable power). Oh well, gotta love Cali right, home of the ****ty watered down **** gas lol.
Old Sep 13, 2011 | 10:49 AM
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True that! Theres a place in Santa Ana that sells 93 and higher octane, but its like $50 for 5 gals.
Old Sep 14, 2011 | 04:28 PM
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You can get 115 at Sears Point AKA Infineon Raceway It ain't cheap either.
Old Sep 14, 2011 | 07:09 PM
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Originally Posted by 04GG
You can get 115 at Sears Point AKA Infineon Raceway It ain't cheap either.
where is that and how much?
Old Sep 15, 2011 | 10:36 AM
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Infineon Raceway Not sure how much because I haven't been there in a while. They have it because they have an NHRA drag strip there in addition to the road course.

Last edited by 04GG; Sep 15, 2011 at 10:38 AM.
Old Sep 20, 2011 | 01:28 PM
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OP is in Orange County so Infinion may be a little too far to get gas.

Nice to see the flame throwers stayed holstered for the most part.

I hope I dont start a huge debate with this one but I personally feel that even when it comes to 91 Octane here in cali all is not created equal.

I use shell cause I have a card there and it SUCKS. The octane rating is not always consistant and I have gotten crap gas from them a few times.

USE 76....They seem to have the best quality fuel with Chevron running a close second.

Always use 91 cause you could very possibly blow your motor on anything less.....
Old Oct 21, 2012 | 02:34 PM
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In Alaska we only have 90 oct
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