I was reading in another thread about using lower octane because of our higher altitude and I found this article about the subject.

Do motorcycles compensate for altitude the same way cars do? I'm curious to try but don't want to cause engine damage over time by riding hard with lower octane fuel.


Colorado's Octane Secret: Part 1

Colorado's Octane Secret: Part 2


In fact, Industry experts say the only research ever performed was done roughly 20 years ago, with carburetor engines.

We even contacted Ford and General Motors in Detroit and experts there say cars with carburetors can run on 85 octane at higher altitudes. But virtually all cars sold since the mid-1980's don't have carburetors and use fuel injectors, which GM and Ford say you should never operate on anything less than 87 octane.

The engines are built to compensate for changes in altitude and they're built to handle a minimum octane of 87 at all altitudes. If you use an octane lower than 87 your engine must compensate even more, which adds more stress to it and could cause damage over time.