Originally Posted by illusion

Close, kinda, sorta, not really.

It's not overall compression ratio, it also has to do with where you are timed, what heat range plugs you are using, piston shape, imperfections in your cylinder, all kinds of things, not just compression ratio. I know it's easy to search google for octane and read what how-stuff-works says and misinterpret it, but actually understanding it is different. Without upping boost a bit I can take advantange of MUCH higher octane than recommended by advancing the crap out of my timing(easy to do for me, plug in a laptop, change a few numbers, watch the wideband feedback to make sure it's happy, then set it as final).

Running too high of octane when not tuned for it acts as if you're running rich, while it promotes catalyst deterioration, running high octane won't have the same effect on the cat as running pig rich, oh like a turbo car(I run about 10.8-11:1). If the catalyst can't change it, it simply gets passed through(the reason many turbo cars belch black smoke even when they are tuned right, and the same reason many of them have multiple cats) any residue with get burned off and the cat will run just fine, although over time it will die faster than a relatively lean car. Now passing lead through the cat is a whole different story. Running too high of octane does not cause

As I said, the easiest way to think of timing is a chemical retard. Low octane = more prone to ignite(timing advance) high octane = less prone to ignite(timing retard). Chemical additives can change the ignition point without changing the effective octane, like lead.