Q. Do I need to use high octane gasoline?
Octane rating is a way to rate a fuel's resistance to knock, which is basically when the air/fuel mixture ignites in an uncontrolled manner due to pressure and heat. Engine knock is potentially destructive and should be avoided. Higher octane fuels have a greater resistance to knock and lower octane fuels offer less resistance. Some people believe that they must use 92-95 octane fuel in their scooters because the manual states that. This is especially common in Chinese scooter owner's manuals. What many scooter owners don't realize is that the octane ratings used in China (and the majority of countries) is different than the octane ratings used in the United States, Canada, and some other countries.
There are two common test procedures for determining a fuel's octane rating, RON (Research Octane Number) and MON (Motor Octane Number). RON and MON are slightly different ways that fuels are tested. RON figures tend to be around 8 to 12 numbers higher than MON figures. Fuels are usually rated at the pump as RON or R+M/2 (RON+MON/2 = an average of RON and MON test ratings) , which is also referred to as AKI (Anti-Knock Index). Because RON numbers are higher than MON numbers, averaging the two to create the R+M/2 rating usually results in a number 4 to 6 lower than the RON number. There is no direct correlation between RON and MON ratings, so in order to know the precise conversion between RON and R+M/2 ratings you would have to know the MON octane rating and that information is usually not available.
RON is the most common octane rating method outside of the US and Canada. R+M/2 is the standard way of stating octane on US and Canadian gas pumps. This is where the confusion happens for many scooter owners. Chinese and other owner's manuals often state the fuel octane requirement using the RON so it is roughly 4 to 6 numbers higher than an equivalent fuel using the R+M/2 method. That means the 92-95 RON ratings in the manual would equate to about 86-91 octane R+M/2 fuel so in most cases regular 87 octane (R+M/2) fuels fit within the specifications and would be acceptable.
Above is the answer by the books, now here is a practical answer. If you are using regular 87 octane fuel in your scooter and you are not experiencing knock then there is no need to use a higher octane fuel. Knock usually sounds like a knock (hence the name) or marbles rattling around in the engine or sometimes more of a tinny rattle. Many stock scooters will operate without issue on regular pump gas, though some will require mid-grade or premium to eliminate knock. Modifications that increase compression or ignition advance are likely to call for higher octane fuels.
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