User-updated map of 93 octane fuel stations

[Chaotic42]

Is there a logical explanation for why the map looks like this?

I think there's some relation between altitude and octane. I know that when I was in Colorado the gas grades were all wonky and low.

 

[Meghan54]

I think there's some relation between altitude and octane. I know that when I was in Colorado the gas grades were all wonky and low.

Air is thinner the higher above sea level you go. Less air going into the cylinders means less pressure at top dead center when things go bang. It's a lot like lowering the compression ratio in the engine, reducing the need for high octane. Cars will run just fine on lower-octane fuel when they're well above sea level.