we also have 87 and 91 thats why a little confusing.....
found this to explain, sounds right?
aus uses the ron measurement
As you know, the "octane number" is a measure of a fuel's anti-knock (or pre-ignition) characteristics.
There are different accepted standards used to measure the anti-knocking characteristics of gas. The octane number you see at US pumps is the average of two such octane numbers; the Research Octane Number (RON) and the Motor Octane Number (MON). This average number is sometimes referred to as the Anti Knock Index ("AKI") or the US Cost of Living Council method ("CLC"). The RON and MON numbers are determined by American Society for Testing and Materials ("ASTM") laboratory tests. Thus, US octane numbers are described as, e.g., 93 AKI or 93 CLC. The equivalent RON number in other countries would be 98.
The RON method determines low speed and low load knock characteristics while the MON method tests high speed, high load, high temperature conditions such as exist during periods of high speed power accelerations, hill climbing, or any period of high power output. The MON method results in a higher octane number & is the more relevant value for racing.
Maybe more than you asked, but ... .
