Motor Octane Number (MON) Another type of octane rating, called Motor Octane Number (MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 lower than the RON, but there is no direct link between RON and MON. See the table below.
Motor Octane Number (MON) Another type of octane rating called Motor Octane Number (MON) is determined at 900 rpm engine speed instead of the 600 rpm fo.r RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 lower than the RON, but there is no direct link between RON and MON See the table below.