What is octane rating of petrols?

Answer 1

Octane rating is a measure of how resistant the fuel is to causing 'knocking' or pre-detonation in petrol(gasoline) engines. It is measured relative to a hydrocarbon which is rated at 100, and determined by testing in a test engine. There are two methods of testing though, which give results called RON or MON. In Europe RON is quoted, and regular petrol is about 92, though usually pumps give 95 RON fuel. In the US a mean of RON and MON is used and for the same fuel the figure is about 5 points lower, so 90 would be the same as 95 in Europe.

Answer 2

Octane is an oil added to gasoline (petrol) to raise the ignition temperature of the gasoline. This is necessary in gasoline engines with high compression as the heat of compression could cause "pre-ignition" in the engine. That is, ignite the fuel before the spark in the engine cycle. This can cause "knock" or a rattling noise in the engine, damage in the engine and loss of power from the engine. Natural or raw gasoline has an ignition temperature of 536F(280C), octane can raise this as high as 804F(429C) at an octane rating of 100.

Answer 3

The octane rating of petrol indicates its resistance to engine knocking or pinging. The higher the octane rating, the better the petrol is at resisting knock. Common octane ratings include 87 (regular), 89 (mid-grade), and 91-93 (premium).