At 21:06 -0500 02/01/19, kilopascal wrote: >It seems so-far the prices betwen Germany and France are very close. The >funny thing is the octane numbers are different. In the US, the octanes 87, >89 and 92 and these correspond to regular, plus and super. > >Is the octane number unitless or is there a hidden metric unit that should >follow? > >John
To make a complicated, non-SI story simpler and shorter : - theoretically the "octane number" is the content in % of iso-octane in a fuel being made of a blend of iso-octane and n-heptane. - in reality octane numbers of commercial fuels are measured in special engines. - there are basically two methods to measure the anti-knocking properties of a fuel : Research Octane Number (RON) and Motor Octane Number (MON), determined in accordance with ASTM D 2699 and D 2700 respectively. Both the RON and MON tests are conducted in the same laboratory engine, but RON is determined under less severe conditions, and is therefore numerically greater than MON for the same fuel. - in the US octane number is given as the average of the RON and MON values, while in Europe only RON is reported. Practically a 92 in the US corresponds to a 96 in Europe. If only we had a SI unit for that ! Louis
