If I was in Denver at 5000 feet and I buy Super unleaded 92 octane and I drive to sea level would my car ping because it would now be more like 88 octane?
Someone told me that fuel rating is altitude adjusted? I could not find any information on this matter.
I've read that the flash point of gasoline blended for cold weather conditions is lower than for warmer weather (winter vs. summer, for instance). This is to aid starting in cooler weather. I'm not sure how, if any, that would relate to changes in altitude, or octane by itself, but it sure seems it might be related since heat is a factor in pre-ignition and detonation.
Volatility and vapor pressure are items manipulated for temperature and altitude. The gasoline must be able to vaporize at lower temps in order for an engine to start. Octane is merely a measure of the resistance of the gasoline to suppress pinging or knock. The octane doesn't change with altitude, but the tendency of any given engine to knock, does. At lower altitudes the air is more dense. There are more oxygen molecules in a cubic foot of air. That denser air can burn more fuel, which produces more cylinder pressure, this makes more power, but also increases the tendency to knock. Generally, the gasoline available at higher attitudes has lower octane than what is available at sea level, because less knock resistance is needed. You probably won't find 85 octane at sea level. but you will in Denver. However, 92 octane bought in Denver will prevent ping to the same extent, at sea level, as the 92 octane gas bought at sea level. If you generally use 92 octane in San Francisco, your engine may not knock on 87 or 89 octane in Denver, but it is likely it will, on that lower octane, when you get down to lower altitudes. It isn't the gas, it's the car, and mother nature.
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Is Gasoline octane rating altitude adjusted?
