Building a 340 engine

Mattax said

Doubt its the same as what we commonly call 98.
If that's the reasearch octane, might be similar to our 92 or 93. Just guessing.
In US & Canada, maybe Mexico, Octane is the average of Motor Octane and Research Octane. Also called the Anti-Knock Index (AKI)

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In the US you use another way of measure octane than we do. I believe you use two different systems, MON (Motor Octane Number) and PON (Pump Octane Number). In Europe, we use RON (Research Octane Number).

I think it is like this 98 Oktan RON is almost the same as 93 Octan PON and 95 RON is close to 91 PON. 95 RON is 87 MOM.