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Old 01-28-2008, 08:03 PM   #1
mikndee
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Member#: 169433
Join Date: Jan 2008
Chapter/Region: South East
Location: jacksonville nc
Vehicle:
2010 wrx
rally blue

Default octane

as long as im posting threads that are ignorant. well i usually put in 93 octane here in hawaii. but what would really be the difference if i just put in 89. the owners manual says to put 93/92. but seriously, obviously the higher octane the better the combustion right? but i kinda want better gas milage since 93 is like 3.50 a gallon on a good day. any ways to optimize gas and performance at the same time.
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Old 01-28-2008, 08:12 PM   #2
oneLEADFOOT
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Join Date: Nov 2006
Chapter/Region: NWIC
Location: Everett WA
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CGM

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I might be wrong but I think it's a waste of money to put 93 oct in your RS. I had a near stock RS for 5 years and always used 87-89 with no problems.
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Old 01-28-2008, 09:40 PM   #3
williaty
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2005 2.5RS Wagon
Regal Blue Pearl

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The owner's manual should say to put in 87 if you've got a 2.5RS like your profile says.

Higher octane gas provides NOTHING but greater resistance to knock. If you're not knocking and the ECU doesn't have the authority to advance timing, then you get NOTHING from running higher octane gas. It just costs more.
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Old 01-28-2008, 09:54 PM   #4
imprexaRS03
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i never put 91 in my rs
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Old 01-28-2008, 10:32 PM   #5
ballitch
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98 cam'd EJ251
Wrx Tranny,slowr than ish

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Waste of money unless you have higher compression, turbo, or mods that warrant using higher octane. You might ping a little more on steep hills, but generally it's not worth it.



~Josh~
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Old 01-28-2008, 11:15 PM   #6
LTracer
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'10 Forester X Limited

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http://en.wikipedia.org/wiki/Octane_rating

Includes a good piece on tuning and how my power comes about from tuning and high compression. Williaty hit it on the head. Higher octane = more resistance to knock = potential for increasing compression/timing. If your '04 RS is stock you'll see very little (if any) tangible gains from anything above 87. Also, premium fuels contain the SAME amount of additives as 87 and haven't be shown to decrease carbon deposits or increase the longevity of the engine.
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Old 01-29-2008, 12:34 AM   #7
rougeben83
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Does it really say Premium in your owner's manual?
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