Octane Number
A rating of the 'knock' characteristics of motor fuels. The octane number is equal to the numerical value of the percentage by volume of iso-octane, C8H18, in a mixture of iso-octane and heptane, C7H16, having the same knock characteristics as the fuel being tested.
The higher the octane number or rating, the greater are the antiknock qualities of the petrol. A rating of how much fuel can be compressed before it ignites spontaneously.
| Heptane | 0 |
| Diesel Fuel | 15 to 25 |
| ISO-Octane | 100 |
| Benzene | 101 |
| Methanol | 108.7 |
| Methane | 120 |
See also: Engine Knock, Tetraethyl Lead, Xylene.
Subjects: Chemistry Mechanical Engineering