I'm aware of low octane causing pinging & that causing engine damage. I always thought that extra high octane was a waste of money, but otherwise harmless. I'm aware of lean mixtures burning valves. I'm aware of hot fuels burning valves. I am not aware of a relationship between high octane & fuel heat. Can you point me to some info on that?
Thanks,
Jim
The problem with high exhaust heat and high octane gasoline is inherent to the fuel blend - high octane fuel is designed to ignite at a much higher temperature to take advantage of high engine compression. It prevents pre-ignition BUT if the engine is not designed for high octane fuel, like the average small engine, the fuel is still burning when the exhaust valves open and the heat envelopes the valves and the exhaust ports. The valves and seats are damaged by heat they were not designed to see. The engine may even produce noticeably less power since your fuel burn was suboptimal and much of it went out the exhaust ports.
You will see this manifested by glowing exhaust manifolds and headers. Back in my sport-bike days we had a guy who decided if 93 octane was good, 103 av gas must be better. He burned up his exhaust valves in a single season. And his bike had less “umph” at top speed where it needed the power to push through the air resistance. Engine manufacturers know the optimum fuel octane rating for their engines, follow their guidance.