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Why is our premium at 94 RON (Sunoco) when the UK is at 98 RON. I understand their gas prices are 4 times more than ours but the choice would be nice.

I would like to see what the performance of the GTO (Vauxhall Monaro in UK) would be like on 98 RON.
 

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It shouldn't be any better, as long as you aren't knocking already. You would have to increase you compression to see a benefit (or maybe advance you timing more).
The higher octane doesn't mean more power in the gas, just that it resists detonating prematurely (knocking), thus allowing the higher compression.
 

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What diverdan said...in some dyno graphs you'll see pulls done on one octane, and then a higher octane with the higher octane making more power (significatly more on boosted engines), it's not the octane that's making the power, it's all the other stuff that was changed to take advantage of teh higher octane....like lots more boost in turbo/supercharged engines.
 

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Yea, what they said... plus, lower octane fuels, at least from what I've heard, contain more "energy" per unit volume from not being refined as much, but don't quote me on that. I had heard at one time that with a car built to run on "regular 87" octane, you'll get worse mileage if you use a higher octane fuel, but again, they could have just been blowing smoke....
 

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The_Goat said:
Yea, what they said... plus, lower octane fuels, at least from what I've heard, contain more "energy" per unit volume from not being refined as much, but don't quote me on that. I had heard at one time that with a car built to run on "regular 87" octane, you'll get worse mileage if you use a higher octane fuel, but again, they could have just been blowing smoke....
I dunno about worse mileage or performance, but maybe not optimal. Older carb'd engines would suffer from carbon build up if too high of an octane was used. The engine simple couldn't burn off all the fuel. In some extreme cases, if you ran higher then recommended octane for too long, you couldn't go down in octane or the motor would knock and ping.

Or so I've heard, Haven't fooled around with carb'd motors long enough, or at least mild-mannered carbs, to really know from experience.
 

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European fuels are rated differently than ours. Their 98 is very close to our 92 octane fuel.
That said and old wifes tales aside, the only way you can increase horsepower with a higher octane is IF THE Spark Maps will increase with octane. As the GTO has been calibrated for 92 Octane, using Sunoco 94 or racing fuel will not increase horsepower. A little talked about fuel metric is called DI ( driveablity index ). All fuels also have a DI index. And as a rule the higher the octane the higher the DI index. While high octane may be good for knock, The higher the DI the more driving ( cold engine ) issues you may experience. That is why it is recommended you use the lowest recommended octane for your vehicle. If an engine is rated to run on 87 octane you will not see an accompaning increase in horsepower ( no increase in command spark )and you might well see more sagging and or stalling during cold engine operation.
 
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