in australia the lowest octane unleaded is 91. the next one up is 95, then 98. there are even a few stations selling 100 octane. but theres hardly any of them, and the price is too dear.
it contains upto 10% ethanol, that helps the octane rating. i would never use a fuel containing ethanol... it rots the rubber fuel lines and causes corrosion in certain meal components. however, newer cars are designed to run with ethanol blended fuel
yeah PB sells 91, 95 and 98.. i use 98 only.. i find with slow driving the extra 5-10% you spend on it over the 91 you make that up in the fact it uses less fuel.. or it seems that way. Without it being tuned gains are very small might get an extra 1 or 2 hp in a small engine but hey its still 1 or 2 hp. Getting it re-tuned for the better fuel will have a large gain though. The higher octane stuff is cleaner too so its better for your car and the environment if you care. I think shell had the 100 octane stuff for a while when they were promoting some race. You can also get a semi racing fuel if you want with 100 or 110 octane rating. But again you need to be tuned to use it to make the most of it. I think over in japan they run 100 octane as their top quality stuff. Most sports imports will suggest you use 100 octane fuel.. pitty its so hard to find so your going to have lower than factory specified power ratings. For the 10c AUS i spend extra to get the 98RON fuel i think it gives a minor power upgrade which is better than nothing and i only fill like every 3 weeks anyway. So its an extra $5 or something a month to use it.