The gasoline and diesel can be compared as follows:
| Properties | Gasoline (petrol ) | Diesel |
|---|---|---|
| Knocking characteristics | In a petrol engine, the combustion rate of air-petrol mixture initiated by sparking of spark plug becomes so fast that the mixture detonates producing metallic pinging sound knocking. |
With a diesel engine, the combustion rate of air–diesel mixture initiated due to compression of air becomes very slow producing a loud sound known as knocking. |
| Octane number | Octane number of given petrol under test is defined as the percentage by volume of iso-octane and n-heptanes which exactly matches the knocking characteristics of the petrol under test. | Diesel oils having high octane number shows higher knocking characteristics. |
| Cetane number | Petrol having high cetane number shows higher knocking characteristics. | The cetane number of a given diesel under test is defined as the percentage by volume of cetane in a mixture of cetane and ∝-methyl naphthalene which exactly matches the knocking characteristics of the diesel under test. The cetane number of a given diesel under test is defined as the percentage by volume of cetane in a mixture of cetane and ∝-methyl naphthalene which exactly matches the knocking characteristics of the diesel under test. |
| Doping agents | Doping agents used in petrol are tetraethyl lead (TEL), crest biphenyl phosphate etc to increase its octane number. | Diesel oil is not blended. |
| Blending agents | Petrol is blended with cracked and reformed gasoline, alcohols, benzene etc to increase its octane number. | Diesel oils are not blended. |