I posted this in another forum years ago
are you confused with your US stickered fuel requirements?
Anti-Knock Index (AKI)
In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the**(, and often written on pumps as*). It may also sometimes be called the**().
in reading this i now have a better understanding for our fuels down under.
ive always ran 98 but after reading this i dont feel so stressed anymore looks like i can go down to 93 using caution if i ever have to.
California fuel stations offer 87, 89, and 91 AKI (91, 93 and 95 RON) so looks like anything in australia above 95 is acceptable with 93 being just below the 90AKI minimum.
I did come across an article a while back that clarified this issue. Multiple tests were performed that proved the value of the different fuels.
The best value (distance per dollar) is from 95 fuel (Oz RON rating). It was also more responsive (better performance) than 91 octane. It also provided longer range per tank of fuel.
The 98 octane provided NO increase in performance but did cost more. The benefit for 98 octane is where an engine can use the higher octane to extract power without pinging, eg. high compression/supercharged/turbo engines. Most petrol Jeeps will get best value/performance from the 95 octane. The SRT may need 98 ???