US gas quality

While a friend was filling up with gas (Australia = Petrol) today, I noticed that their regular, plus, and premium fuels had octane ratings of 87, 89, and 91 respectively. In Australia, it's 91, 95, and 98, meaning that our regular fuel in Australia is equivalent to the 'premium' fuel in the USA. As an aside, regular fuel is currently selling for $2.069 per gallon, or $0.547c per litre, to three decimal places.