Different octane ratings to different states?

All grades of gasoline are lower in the high-altitude areas of some Rocky Mountain states. This is because the octane requirement of older engines without engine control modules decreases with altitude. At higher altitudes, these engines perform as well on the lower-AKI gasolines as they would at sea level on higher-AKI gasolines.

Octane is added to prevent pre-ignition, being that the volume metric pressure is lower at altitude less octane is needed at higher altitudes. In years past lead was the pre-ignition preventive additive.

the closer u r to sea level the less octane u need....going up and down mts is more strain on motor and requires more octane not to ping.

here in pa.,where i live,they have 87,89,and 93 octane.