Modern GDI engines also cooldown the intake charge by spraying some fuel as the valves open to allow air in, specially if you have something like bmw valvetronic, nissan vvel or toyota valvematic in the system as it creates a very high pressure area as the valves crack open (no throttle blade), then add some variable valve timing to add more control and precision to the ignition events. Due to having clean emmissions they can market to a lot of areas and by squeezing more power by designing it to run on higher octane oxygenated fuel they can achieve more power with lower cc so that is another win for them.
Those engines are usually tuned to extreme and provide close to supercharged engine power levels while being NA and have very clean emmissions too.
Btw no petroleum distiller ever markets their higher octane fuels as “better”, they market their detergency package which is in all their gasoline fuels which results in better cleaning, whether its regular 87 MON or 93 MON.
So in a nutshell, your average egg and potato cheapass toyota corolla engine wont benefit from anything with higher octane, all it will result in is bad fuel mileage (slow burn), more deposit (slow burn), damaged cat (slow burn) and oil contamination (slow burn)
For fuel requirements, its best to contact manufacturer of engine as its not just one simple formula anymore. They have spent quite a lot of effort to make sure the fuel requirements are correct, specially for a cheapo commuting econobox shopping trolley car like a corolla or civic. Their global sales will take a nosedive if they started recommending expensive fuel and engine oil requirements.
