Do I have to use Premium Fuel at high altitude - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-20-2006, 10:11 PM   #21
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Quote:
Originally Posted by fantastic88
What is the reason for the drop in octane at high altitudes? Is it cause the slight change of oxygen would cause a rich condition?
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Old 04-20-2006, 10:13 PM   #22
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Off the top of my head (no research) I'd say the lower pressure air lowers your effective compression a bit, so you don't NEED the higher octane to prevent detonation.

Higher octane fuel ignites at a higher temperature. It does NOT add power by itself. Some of our modified cars benefit from much higher octanes when we advance timing quite a bit to prevent detonation.
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Old 04-20-2006, 10:25 PM   #23
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Thanks for the correction, Bill

I guess my overall point is that you should run 91, 92, or 93 (whichever is the "Premium" fuel at the gas station) whenever possible, but if 90 is the best they have to offer, definitely choose it over 89 or 87.
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Old 04-21-2006, 12:51 AM   #24
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Modify your car and keep stock pulley and you should be able to run a lower octain. The scanner will be your friend with that though.
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