Quote Originally Posted by 4 MARIE View Post
your ST will kind of "dumb itself down" to whatever octane fuel you are using. Which is handy if you are ryding in Mexico for example.
So while it won't be performing at 100% it will not suffer any real problems.
A common mis-conception.

While it might not ever be a problem with a Spyder because the compression really isn't THAT high........

There are two kinds of combustion chamber pre-ignition (ping or knock).

When the spark hits, if the fuel burns too quickly there is an explosion of sorts. This "spark knock" is what the engine can correct for by backing off the timing a bit.

Then there is compression knock, which is much worse and, if present, can NOT be corrected for with simple ignition timing changes.
With compression knock, the fuel ignites BEFORE the spark hits and the max. expansion occurs before TDC and puts a huge strain on the engine.

Having a higher octane helps prevent both these conditions but really is the ONLY protection from compression knock if conditions can occur to cause that. Note: A very sophisticated engine could correct for that too by changing the valve timing but I don't know if any actually DO that or not, since using the right fuel would make it mostly unnecessary.