Ethyle petrol as sold commercially contains one part tetra ethyle lead in 1,300 parts of petrol. It enables an appreciable higher compression to he used without detonation occurring. The performances of engines using ordinary fuels have been improved by adding stabilizers or “anti-knock constituents” to them.
The octane rating of gasoline is a measurement of the fuel’s ability to resist knock or ping. A high octane rating indicates the fuel with not knock or ping easily. It should be used in a high compression or turbo charged. A low octane rating gasoline is suitable for a low compression engine.
Octane numbers give the antiknock value of gasoline. A high octane number (91) for example will resist pin better than gasoline with a low octane number (87). Automotive makers recommend octane number rating for their engines. The owner’s manual will give the octane number recommended for the cars’ engine.
Gasoline grades indicated antiknock value of gasoline
Premium Gasoline = High Octane, High Antiknock 95 Octane
Regular Gasoline = Low Octane, Low Antiknock 87 Octane
If the Octane Value of a fuel is increased the compression ratio can be raised and for each octane value there is a corresponding compression ratio that can be employed before detonation begins.
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