According to wikipedia - United Petroleum sells 100 RON unleaded fuel (10% ethanol content) at a small number of its service stations (originally only two, but it has now expanded to 19 outlets).

My friend drives a black DC5R.

Those are interesting and true facts you brought up Gumus89. But lets say the car had an aftermarket ecu like a KPRO, that can detect the extra knock resistance and advance timing. Cause my friend does have one, and maybe thats why I can feel the "extra ompf'. I'd imagine all recent cars with their ecu's would be able to advance timing especially Honda's because Japanese petrol is 100RON