Over here in the UK, if you buy petrol from the garage pump, you get 95 octane as standard.  The same in the other bits of the EU that I've seen.  Its also sold in litres, so a % figure or ratio would be helpful.  Does 8oz to 1USG work out to 1:16 or about 6.25%?  87 octane is something I remember from back in the '60s, and was known as "commercial", but I can't remember when I last saw it.