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Old 01-04-2011, 07:29 PM   #76
Scooby Newbie
Member#: 250463
Join Date: Jun 2010
Location: Evanston, Il
2010 Impreza 2.5i


I use 89. My Impreza is the only car I've ever had that had a noticeable improvement in drive quality (purely subjective) by switching to a higher octane.

Also, what does IAM stand for? If you'd like to explain the corresponding numbers, too, that would be fine.

Thanks in advance.
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Old 01-09-2011, 05:42 PM   #77
Scooby Guru
Member#: 134005
Join Date: Dec 2006
Chapter/Region: MAIC
Location: Pittsburgh, PA
2004 WRX Premium


I agree with those of you that claim your engine 'runs better' on 89+. I personally only use 89 since it's 10 cents more than 87... 93 is 40 cents more I believe, which is getting a bit too high for me.

If there is any gain in power, it is very small... but that's not the point, the point is it doesn't have that piston slap as much and just overall sounds better. 89 FTW.
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Old 01-09-2011, 06:05 PM   #78
Scooby Specialist
Member#: 6295
Join Date: May 2001
Location: Portland
2016 WR Blue WRX #7


it's all about the detergents/additives in gas...

crappy gas from places like Arco or grocery store stations don't have have the additives the top tier gas uses and will dirty up your engine more than gas from Chevron, Texaco, Shell, 76, etc.
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Old 01-10-2011, 12:08 AM   #79
Scooby Newbie
Member#: 260372
Join Date: Oct 2010
Chapter/Region: NWIC
Location: Redmond, WA
2012 OBP STI 5-Door


I have been keeping track of every fill up what location and octane rating of the fuel since i bought my car in july. At almost 17,000 miles I will start using 93 octane throughout my whole next oil change interval(3000 miles) and see if cumulatively there is any change on my 2011 2.5i just out of curiosity.
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Old 01-11-2011, 06:24 PM   #80
Scooby Newbie
Member#: 268319
Join Date: Dec 2010
Chapter/Region: MWSOC
Location: St. Louis, MO
2011 Impreza 2.5i
Marine Blue Pearl


I better quit using the cheapo 87 on my brand new '11...maybe I'll switch to 89
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Old 01-11-2011, 09:06 PM   #81
Scooby Newbie
Member#: 269978
Join Date: Jan 2011
Chapter/Region: NWIC
Location: WA
99 turbo legacy
sandstone metallic


I use 92 and octane booooster, I also have a turbo, but! It quiets any slap down.. Not that there really ever was..

In its N/A days It idled like *****! so I would use 92 with slight improvement, but not a huge difference. (Its gas.................I dont really know)
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Old 01-11-2011, 11:12 PM   #82
Scooby Newbie
Member#: 165087
Join Date: Nov 2007

husky/mohawk isnt in the list of top tier gas.
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Old 01-12-2011, 01:49 AM   #83
Scooby Newbie
Member#: 145195
Join Date: Apr 2007
Chapter/Region: MWSOC
Location: Illinois
2007 Impreza 2.5i
Urban Grey Metallic


I will further add to the discussion of 87 Minimum translating to 87 octane is the lowest octane to use and you may need higher depending on driving habits/weather/elevation...

89 in my 2.5i and it runs without knock compared to 87. Ive run 93 but dont notice any added benefit.

stock motor

30mpg highway

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