Does your manual say 91 RON or 91 API? The method of computing the octane rating is different around the world.
The label on the bikes usually say 91 RON, which is 87 API.

 

Hey:

Yes RON, fixed. RON (Research Octane Number) is the world STD rating, the USA/Canada also uses AKI (Anti Knock Index) or PON (Pump Octane Number) displayed as (R+M)/2). This does not account for Gasoline fuels used in the MTN region of the USA REG that are only 90 RON(85 AKI) or the MidWest with 94 RON (95 AKI) Gasahol that your bike will run like Do do on. I should have stated RON/PON is diff and 87 is ok in the USA/Canada. But only if it meets the less than 5% Methanol & 10% Ethanol criteria.
Also (API) American Petroleum Institute is used in Oil and Natural gas as a Quality std, and is not for Gasoline or Other fuels, as they already had an established rating system.

My point was, it is listed in the Owners Manual for that year. Atleast mine it is.

Dub

 

I have no idea why Honda makes recommends for fuel in RON for the bikes sent to the US. It just confuses people. They don't know that RON and AKI are different, and our fuel is labeled in AKI on the pump.

 

Hey:

And 3 of my bikes were made here in the USA in Ohio and still have that info listed in RON As does My new Civic and the manual was printed here too, so go figure. Too worldwide corporate minded, they get confused I guess.

Dub

 

And yet they can manage to put US emissions stickers and such all over them when they are targeted for distribution here....