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Old 12-28-2006, 08:23 PM   #1
illegal2.2
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Default anyone running NON-OXY premium gas?

from what local subaru members say, it's good for their car. BTW they have mainly wrx. just wondering if running non oxy in MY97 gt will benefit from more gas mileage and power? lmk guys. thanks

choung
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Old 12-28-2006, 08:56 PM   #2
gtwagon941
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are you talking about fuels like E-85? Never heard of "non-oxy"
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Old 12-28-2006, 11:39 PM   #3
iamrazor
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I think you mean oxygenated fuel? That's primarily used in the northern states during winter months for some reason that escapes me at the moment. Sorry, I've been up since 5AM.

generally it drops a few MPG per tank.
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Old 12-28-2006, 11:48 PM   #4
ten80
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They add 10% ethanol to help reduce emissions and the winter "brown cloud" that occurs because of cold air pockets trapping polution. it does reduce your mileage because it is the carbon in gasoline that provides energy for combusition, not oxygen. You will indeed have more power and get higher mpg, however, you shouldn't run premium unless you have high compression or turbo engine. This is because premium has a higher octane rating (more oxygen) and contains less energy for combustion, which is useful for reducing detonation in the applications mentioned. i've been running 85 octane for a while now with no hiccups in my 2.5L impreza- our motors are not very picky!
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Old 12-29-2006, 12:41 AM   #5
Wiscon_Mark
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It'll improve MPG because of the items listed about oxygenated gas, but I dunno where you'll find it up here during the winter...
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Old 12-29-2006, 12:56 AM   #6
MCarp22
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Quote:
Originally Posted by ten80 View Post
This is because premium has a higher octane rating (more oxygen) and contains less energy for combustion
Octane rating has nothing to do with oxygen content or energy, and everything to do with how much you can compress it before it ignites.

Quote:
Originally Posted by ten80 View Post
you shouldn't run premium unless you have high compression or turbo engine.
You don't necessarily need honda-like 11:1 compression to take advantage of premium fuel. I believe some of the DOHC 2.5s took premium from the factory due to aggressive igntion mapping.
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Old 12-29-2006, 01:04 AM   #7
Wiscon_Mark
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Quote:
Originally Posted by MCarp22 View Post
You don't necessarily need honda-like 11:1 compression to take advantage of premium fuel. I believe some of the DOHC 2.5s took premium from the factory due to aggressive igntion mapping.
Only the 96 GT (and LSi??). And it didn't really make all that much power.
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Old 12-29-2006, 01:11 AM   #8
ten80
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I have to admit that you are correct, octane is C8H18 and has no oxygen content- I'm not sure what I was thinking . Also, I was misinformed about the energy content. It really depends on the formulation of the gasoline and the ratio of carbon-carbon bonds (high energy) to carbon-hydrogen bonds (low energy). I was correct about ethanol reducing energy yield though

I've not heard of USDM 2.5L dohc needing premium fuel, wich is interesting because subaru's tuning is generally very conservative.
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Old 12-29-2006, 08:24 AM   #9
MCarp22
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Quote:
Originally Posted by Wiscon_Mark View Post
And it didn't really make all that much power.
My neon didn't either.
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Old 12-29-2006, 09:12 AM   #10
xcntrk75
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I avoid it... It's everywhere around me, hard to find non "winter gas" in my crowded area. I avoid it strictly cuz I'm tuned on 93 octane (non ethel) fuel and using it will change my fueling...
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