We use (RON + MON)/2 to get an octane rating. Since Australia (as well as Japan, Europe, etc.) is RON only. Our 91 is comparable to your 96. Most states have at least 92 or 93 at the pump here which is 98 down under.

Conversion examples:

US 87 = Aus 91 (RON 91 MON 82.5 R+M / 2 = 86.75)
US 89 = Aus 95 (RON 95 MON 85 R+M / 2 = 90)
US 93 = Aus 98 (RON 98 MON 88 R+M / 2 = 93)

More info at this site:

http://www.autospeed.com/cms/A_870/article.html

 

im currently paying $2.45 a gallon of premium and there 100 octane at the pump but its $6.00. i got only 250 on my last tank