In an alt.home.repair thread, some were proposing 92 AKI gasoline for lawn equipment, where I questioned the logic, based on compression ratio alone.
AFAIK, the octane rating just means the gas reacts differently to a given compression ratio (and other detonation factors such as heat & timing).
For example, given whatever the compression ratio in my lawn equipment is, I get along just fine with 87 AKI California gasoline; yet some propose 92 AKI fuels instead.
My question: Of the engines that *require* high-octane fuels, is the (main) *reason* for that requirement the compression ratio? [We can ignore detergents for this discussion.]
Or are there other factors (ignoring heat & timing, which are a given) that increase the need for fuels rated at a higher anti-knock index?
Restated: Q: Is the *need* for premium directly in proportion to the compression ratio of the engine?