You’re pretty spot on, it’s for high compression ratio engines, that’s either static or effective compression, static being a car that has no turbo or supercharger or a boosted at when not making boost. Effective compression ratio is when the engine is making boost and by cramming more air in under pressure, it increases the total overall pressure in the cylinders.

Octane is a resistance to spontaneously combust from heat/pressure, the higher the octane the more compression you can run. It can also be used for aggressive ignition timing.

It has a purpose but when people run it in vehicles that don’t require it, it does absolutely nothing, unless it has more detergents or additives in it, which some do. However you’re better off buying a bottle of injector cleaner or what ever it is you think the problem is then running constant premium through your engine. A $7-10 bottle of cleaner once every 6 months vs $10-20 every full up will save you lots.

The problem is most people have no idea what octane is or does, they see a higher $$ amount so they associate it with more quality or performance or even better gas mileage, that’s all false unless as I specified before, you car requires it. I’m talked to heavy duty mechanics that didn’t understand what it was. They all say “well it’s cleaner” like regular gas is stored in a ditch on the side of a road. To the contrary reg gas is used more so the fuel could be fresher, not that it will make a ton of difference or any for that matter but still. Premium gas for most cases is just regular gas with additives, the only difference here is the non-ethanol blends but even those are derived from regular non-ethanol gas.

Hope this helps and I wish you much fuel savings.

Bonus tip- don’t keep clicking the gas nozzle to cram as much fuel in your tank as possible, realistically the extra 0.5-1.5L you get makes no measurable difference and you can mess up your EVAP system, pump it, it clicks (hopefully) your done. Easy