The difference in octane generally indicates the resistance to detonation. It has nothing to do with compression ratio. So throw the idea of the compression ratio out the window.

A car mostly cannot change its compression ratio, but it can advance or retard the ignition. It does this in concert with the O2 sensor for AFR and knock sensor.

eg; If a car senses it is using a lower RON than what is recommended due to the detection of knock and pinging via the knock sensor it starts to retard timing, which lowers the power. And if it detects that knock is 0 and AFR meets the target it gets more aggressive with the timing advance.

But, no. On normal cars, the car will go no more aggressive on the timing than it's stated RON target. If your car maker recommends a RON91 you gain nothing by going to 98 as the ECU will go no higher to preserve the engine from blowing holes in your piston.

If you own a performance car with a wide range of recommendations, then yes, you can try different fuels.

My Mitsu Evo in the manual says that it will run on 95 to 98, so maximum power is achieved at RON98.
My BMW says it will run on 91 to 98, so being a cheap bahgger I isi with cheapo petrol RON91 to jimat.

Under law, all fuel contains a certain amount of detergents. Some fuel sellers to increase sales put more additive in their premium RON97 petrols, but not all of them.

Also if you use a direct injection engine, all this cleaning shit is useless.

Proton, probably 95 is fine.

Uni of Lolyat?

I have to admit I'm an electrical and not a mech lol.

I can't even tell the difference between a stock GT-86 and one with a tuned Tomei exhaust in terms of performance. The general rule is that most people can't sense a difference in power till it hits the 10 percent power mark.

Your butt dyno must be incredibly sensitive.