[mobythevan]

It is not that simple. Higher octane allows higher compression which in turn allows more power per unit of fuel to do work and not get wasted out the exhaust or as heat into the engine cooling system. So an engine built with low compression cannot really make use of high octane fuel like you say. However, an engine with high compression can use high octane fuel more efficiently and produce more useable power per unit of fuel. Higher octane has a purpose. Slow burning fuels allow more power to be useable and not wasted in a piston engine. Quick burning fuels (low octane) lead to more wasteful piston engines. It is more of an engine design question than what fuel to put in your tank.