Why do you have to burn low octane gas at high altitude?

Answer 1

Now i am notentirely positive, but its because high octane fuel burns easier, so the jet engine doesn't need to be very complicated to work in the air. Also the air up i the atmosphere has a less concentrated amount of molecules, i don't know why that has something to do with the high octane gas but, you never know. And the higher octane needs less, to do more. So it makes the plane lighter and can hold more.