IMO the ECU is not smart enough to reduce timing for 95 oct fuel. It has a knock sensor in the middle of the valley, and if that senses too much knock, it will retard. It doesn't sense your fuel and adjust.
The knock sensor doesn't work very well either, as shown by the fact we had a car with a hole through #6 piston to replace the engine on, from too much det.
4 cents a litre, or risk having to change a motor if you get it wrong. I know what I'm doing.