So, the way I understand it is, in the US we use the anti-knock index which is an average of the RON (research octane number) and the MON (motor octane number). Most of the rest of the world uses the RON. The RON will list about 4 to 5 points higher than the AKI for the same fuel. So in Europe, and most of the rest of the world, 94 octane would be about the same as 90 octane in the US.
Clear as mud?
Clear as mud?