At elevations above 3,500 feet, the air is less dense, which affects how engines combust fuel. Because of this, the risk of engine knocking — where fuel combusts prematurely — is lower at higher altitudes. This allows vehicles to safely run on lower-octane fuel without facing performance issues.
Fun fact, if you go somewhere with high elevation your going to see lower octane ratings. Colorado for example. https://www.slashgear.com/1825420/colorado-85-octane-gas-reason-substitute-87/
That is, and I say this completely sincerely, both the coolest and most fun fact I’ve learned all week. Thanks for sharing!