Oktaaniluvulla

Oktaaniluvulla is a concept related to the combustion properties of gasoline. It quantifies the fuel's resistance to knocking or pinging during combustion in an internal combustion engine. Knocking occurs when the fuel-air mixture in the cylinder ignites prematurely and uncontrollably, leading to a sharp sound and potential engine damage.

The octane rating is determined by comparing the fuel's anti-knock properties to those of two reference fuels: isooctane and n-heptane. Isooctane, which has excellent anti-knock properties, is assigned an octane number of 100. N-heptane, which knocks easily, is assigned an octane number of 0. A gasoline's octane rating is then expressed as the percentage by volume of isooctane in a mixture with n-heptane that has the same anti-knock performance as the gasoline being tested. For example, gasoline with an octane rating of 90 would have the same knocking tendency as a mixture of 90% isooctane and 10% n-heptane.

Higher octane fuels are generally required for engines with higher compression ratios, as these engines operate at higher pressures and temperatures, making them more prone to knocking. Using a fuel with a lower octane rating than recommended by the engine manufacturer can lead to knocking, reduced engine performance, and potential long-term damage. Different regions may use slightly different scales or methods for determining octane ratings, such as the antiknock index (AKI) used in North America, which is the average of the Research Octane Number (RON) and the Motor Octane Number (MON).