The octane number is one of the basic indicators of gasoline quality. While in the combustion chamber, gasoline is exposed to high temperature and pressure, which can lead to the self-ignition of fuel, which is manifested as engine knocking and causes damage to the engine. The octane number shows the resistance of gasoline to self-ignition. Its name is derived from the hydrocarbon octane, which is highly resistant and is taken as a reference, its assigned octane number being 100. There are several methods to determine this parameter; the Montenegrin standard prescribes the research octane number (RON). Modern engines require gasoline with an octane number of 95, and Jugopetrol offers RON 95 and 98 gasoline, both ratings being unleaded.