I imagine the engine is optimized to run on "average" gasoline for a given octane level, tuning compression ratio, spark timing, air mixture, etc.

I'm not an ICE engineer, so I would love to know how much of a performance change can be expected from this guy's machine.

You might find this youtube channel interesting: https://www.youtube.com/channel/UC2rzsm1Qi6N1X-wuOg_p0Ng/vid...

He has run a gasoline engine on a whole slew of fuels, including some that may be surprising, such as isopropyl alcohol, various solvents, crude oil, and a 50% diesel gas mix.

Gasoline engines can also run on pure propane, but the fuel pump, tank, and some other parts do need to be replaced.

I guess the point is that gasoline engines are not in general super sensitive, while they still could be more optimized for certain fuels.

Thats a low compression mower engine. Modern automobile engines are indeed quite sensitive to predetonation from slower ignition times offered by most alternatives without being designed for them.

>Modern automobile engines are indeed quite sensitive to predetonation from slower ignition times offered by most alternatives without being designed for them.

If by "design" you mean a different cam profile to drop the dynamic compression ratio then sure.

Maybe this can be handled by adjusting valve timing in software.

I believe the tuning is controlled electronically through software (this is what enabled VW Dieselgate). So a software update could enable the vast majority of cars to be able to use this fuel.