Some info contained here:

http://www.pcf.ab.ca/quick_answers/gasoline_general/octane_rating.asp

And here:

http://www.shellus.com/products/product_info/gasoline_properties.html

"Probably the most familiar gasoline characteristic is antiknock quality or
its octane rating. The octane rating is simply a measure of the gasoline�s
resistance to knock. Knock is the sound made when the fuel/air mixture in
the engine�s combustion chambers ignites by itself (auto-ignition), either
before the spark occurs or in front of the flame already started by the
spark plug. Advancing ignition timing increases the tendency to knock. "

It says absolutely nothing about the higher-octane gas burning at a higher
temperature.  It does say, however, that engines with higher compression,
such as Euro-WBX, or advanced timing, such as mine, will benefit from a
higher octane gasoline.  Also, engines with combustion chamber deposits,
such as any old WBX, will have slightly higher compression ratio, hence the
benefit of increased engine longevity from higher-octane gasoline.

All of this should be considered along with the driving environment.  It
seems that an engine under higher and prolonged loads, such as a
hill-climbing Westy, is probably going to benefit from the more expensive
gasoline.

Chris.