interesting conversion i found

In Europe 98-octane gasoline is common and in Japan even 100-octane is readily available at the pumps, but this octane nomenclature is misleading to Americans as foreign octane ratings are derived entirely differently from our own... So, like every other measurement system it seems that everyone else uses a different scale than we do, but unlike most other instances where we have had the good sense to create different units of measure in this case we all use the same name...
Japan and Europe use a system called RON or Research Octane Number to determine the octane rating of their gasoline, while stateside we use a system called AKI or Anti-Knock Index to determine gasoline's octane rating... Interestingly, to further complicate things it would seem that our own AKI system is actually derived from the average of the RON system and another more complicated system referred to as MON or Motor Octane Number... So, to recap our methodologies for measuring gasoline's octane rating are different, but share some common elements...
So, with the commonality of RON in mind a good rule of thumb is as follows, multiply the foreign RON Octane rating by 0.95 and you will have the US AKI equivalent.

( RON Octane Rating x 0.95 = AKI Octane Rating )
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

So, as you can see the 93 or 94 octane fuel we are all paying an arm and a leg for is actually quite comparable to the higher octane fuels found in Europe and Japan. The people whom have to worry about low octane rating are our friends out west in places like California that are subjected to substandard 91 octane.
91 AKI Octane (US measure) = 95.5 RON Octane

credited to
Originally posted by E_SolSi@Jul 17 2005, 12:48 AM
this is not my post just a post i found that i thought i should spead so more people knew.

Quite comparable? Yes they're the same basic gasoline, but we pay no where near as much as Europe or Japan pays - now around $7 per gallon in Europe.

yeah i thought it was interesting because i got into an arguement with a guy i work with. he was trying to tell me that i there is no need for my b16 to run off of 91. he was saying that it would run fine off of 89. ha crazy kids.everyone knows that b16's and other related si engines are ment to run off of 100(japan). so i did a search and found this. so it shut him up. thought it would be useful for others.

i need 95.....no more mixing race fuel and premium