Here are some thoughts about the ongoing discussion on all "motorhead" forums about high octane gas:
- The only real advantage of "race" gas is, that it may not have any ethanol in it.
- Most all gasolines, even race gas, do not contain lead anymore, which may be important for older engines and valve seat durability.
- Higher octane has a drawback:
Higher octane numbers are achieved with ignition retarding additives
This means there are less carbon-hydrate molecules available to provide energy and thus performance
Higher octane numbers mean that the combustion process is less prone to detonation which occurs at higher compression ratios
If your engine, based on the specific compression ratio, will not require a higher octane rating, stick with the gas that gives you what you need.
Anything beyond that is a waste of money and could probably cause issues with unburned gas washing away the oil on your cylinder walls.
Race gas does not make horsepower. It prevents a high compression engine from detonation.