Well let's see. When I was pumping Sunoco 260 back in '79 at my part time job it was rated at 106 octane. I think the octane rating might just have something to do with detonation. Unleaded fuels have a lower octane rating primarily because of the absence of lead. In addition today's pump gas may contain oxygenates and/or alcohol. I suppose you could argue that good combustion chamber design, piston dome shape, valve layout, etc. can alleviate some of the effects of crappy gas, but I think most manufacturers have known for a while that high cylinder pressure and modern fuels are a recipe for disaster.