From memory you can't actually buy anything less than 95ron in the UK. The choice is generally 95 (cheap stuff) or 98 (for those who love their engines). Selling 91 at the pumps is just the Petrol Company's way of saying F**k You New Zealand.

I use the Mobil 97.5 .....'sgot a brand name on it (that I can't remember) but then so does beer and I only ever look at the %age alcohol on drinks.