Definitions for "Octane number"
Indicator of capacity for a product to resist high pressures without spontaneous combustion occurring also known as resistance to knocking. When the numbers were first developed, the researchers found that normal heptane (a hydrocarbon) had almost no ability to resist knocking so they gave it an octane number of zero. Then they found that isooctane (also a hydrocarbon) was very resistant to knocking so they gave it the octane number of 100. To measure a particular sample of gasoline they discovered when it began to create detonation. Then they mixed isooctane to heptane to find out what percentage of isooctane created the same results as the sample of gasoline. There are two methods for determining the octane number depending upon operating conditions. The Research Octane Number (RON) is obtained when conditions are somewhat mild. The Motor Octane Number (MON) is obtained when conditions are somewhat severe and give a much lower number than the RON.
Measure of the anti-knock qualities of a gasoline fuel.
A term (Motor Octane Number) devised by Graham Edgar in 1926 to measure the anti-knock quality of gasoline. The octane number of a given fuel is the percentage of iso-octane (octane number: 100) in a blend with n-heptane (octane number: 0) with the same anti-knock properties as a sample of the motor gasoline being tested. A high octane fuel has better anti-knock properties than one with a low number. A similar but improved method (Research Octane Number) was developed in the late 1930's.