What does the Octane Number at the pump mean?
MTBE The octane rating of a fuel is what most people are familiar with, but there seems to be a lot of confusion surrounding it. In simple terms the octane number you see at the pump is the average of two octane numbers; the Research Octane Number (RON) and the Motor Octane Number (MON) or (RON + MON) / 2. This final octane number is sometimes referred to as the Anti Knock Index or AKI. This pump octane number is a measure of the anti- knock characteristics of a given fuel. MON and RON are determined by standardized ASTM laboratory tests. The details of the tests are not as important as what they mean in terms of performance. Low to medium-speed knock characteristics are determined by the Research (RON) method, while high-speed and partial throttle heavy load knock characteristics are determined by the Motor (MON) method. MON testing is conducted under more stringent conditions with the timing on the test engine advanced and run with a higher inlet air temperature, so the MON number te
