The octane number of gasoline is one of the most important measures of gasoline quality to predict accurately the octane ratings of blending gasolines. This measured on a scale that ranges from that equivalent to isooctane (octane number of 100) to that of n-heptane (octane number of zero) octane no is effected by the saturates, aromatics, and olefins contents of gasoline. We take it as a standard and measure octane number by comparison with this standard. The accurate octane blending method will optimize the blending of gasoline components, when gasoline components are blended together, we will calculate the octane number of the blend with different octane number of the component or if the four components are of equal octane number. The blend octane number may be greater than, equal to or less than that calculated from the volumetric average of the octane numbers of the blend components, which indicates nonlinear blending. Blending would be linear if octane number of a blend was equal to that predicted by summing the octane numbers of the components in proportion to their concentrations. In practices, the discrepancies between the octane numbers of blends and the linearly predicted values have been correlated by specific empirical equations and these have been used to correct the linear predictions.