Octan number
The most important characteristics of gasoline is the octane number, a measure of gasoline's ability to resist combustion early (road engine). This number is measured for a mixture of 4,2,2 - trimethyl pentane and that - heptane. For example, 87 octane gasoline has meant that the efficiency of the operation of such a mixture of 87% ISO-octane, 13% that - heptane.
This system has been done by Russell Marker.