Many factors significantly increase an engine’s octane requirement. ‘I’hey include a higher compression ratio, a bigger cylinder bore, leaner mixtures, higher coolant and intake-air temperatures, dry air (low humidity), higher barometric pressures, altitude closer to sea level, and more spark advance. Also, cast-iron heads need more octane than aluminum heads. As engine temperatures increase, a higher octane gasoline is needed.
The benefit to using a 100-octane gasoline in high-performance engines goes beyond the octane number. The distillation curve of the gasoline defines the temperature at which various amounts of gasoline are evaporated. Gasoline must be in a vapor form to burn, so the more readily it vaporizes (within limits), the better it will work in your engine. This can be a performance benefit in some engines because of the ability of the gasoline to evaporate more readily, contributing to more complete burning, which in turn leads to greater efficiency and power.
Many manufacturers put knock sensors on engines. When the knock sensor senses detonation, it sends a signal to the main computer, which retards the spark timing until detonation ceases. This can cause spark-timing retard, which reduces horsepower and fuel economy. Detonation normally occurs in one or sometimes two cylinders unless a serious fuel-starvation problem exists. Most engine-management systems reduce the spark timing in all cylinders, although some reduce the timing in only the cylinder that is detonating. Using a gasoline high enough in octane to satisfy the engine under all types of conditions will ensure maximum performance from all cylinders.
via: totalmotorcycle.com