Almost all products from a fuels refinery, even asphalt, are blended using intermediate streams to produce a variety of on-specification finished products. Gasoline blending is the most complex and highly automated blending operation, with other products usually involving less automation and modeling. The objective of product blending is to allocate the available blending components in such a way as to meet product demands and specifications at the lowest cost while maximizing profit. Butane has a high blending octane number and is a very desirable component of gasoline; refiners put as much in their gasolines as vapor pressure limitations permit. Vapor pressure blending indices (VPBIs) are compiled as a function of the Reid vapor pressure of the blending streams. Octane numbers are blended on a volumetric basis using the blending octane numbers of the components. A special blend of gasoline is produced for blending with ethanol at the distribution point.