Questions and Answers
Gasoline Octane
Q. I recently purchased a 1988 BMW 75Oil (12 cyl, automatic) and the Octane requirement is 91 RON. OK, but since I must go by the pump method and that is RON+MON/2 and I don't know the MON. How do I determine, except by the preignition method, what the pump octane requirement is?
Confused in Virginia
RichardA. RON or Research Octane and MON or Motor Octane are numbers used by the fuel companies to determine the octane rating of a gasoline. In real life they mean nothing to the guy who pulls up at the pump. This is for Federal and State Agencies to determine if the octane rating on the pump, i.e. 87, 89 or 91, is accurate. Inspectors test the gasoline in the gas stations tank on a regular basis (they check me every two months) to be sure the consumer is getting what they pay for.
Basically if it says 91 octane on the pump, it is at least 91 octane. My 91 actually tests out at 93.
