Research Octane Number (RON) and Motor Octane Number (MON) are two different physical tests to determine an effective "octane" rating. Typically MON reads about 8-10 points lower than RON for a given batch of fuel; this difference is called the fuel's "sensitivity".
The rating that US pumps use is called AKI, or Anti-Knock Index, and it is the average of the RON and MON rating for that fuel. Some pumps are even labeled "(R+M)/2".
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Research Octane Number (RON) and Motor Octane Number (MON) are two different physical tests to determine an effective "octane" rating. Typically MON reads about 8-10 points lower than RON for a given batch of fuel; this difference is called the fuel's "sensitivity".
The rating that US pumps use is called AKI, or Anti-Knock Index, and it is the average of the RON and MON rating for that fuel. Some pumps are even labeled "(R+M)/2".