If a conventional gasoline station sells three grades of gasoline, typically it must have at least one storage tank for each grade.
Moreover, each dispenser hose is usually limited to the dispensing of a single grade of gasoline. The objective of the blending pump is to introduce greater flexibility into this situation: to give the motorist a wider choice as to the grade of motor fuel he will buy, and to give the station owner an option of using fewer storage tanks.
Blending pumps have been available for nearly half a century. They look much like conventional pump island dispensers. However, instead of being piped from a single storage tank, a blending pump is piped into two tanks–one containing low-octane gasoline, the other high-octane.
When the motorist pulls up to the dispenser, usually by pushing a button–the octane rating of the fuel he or she desires to buy.
This action, in turn, programs the dispenser. Fuel from two tanks is drawn into the dispenser, in proper proportions, and mixed in the meter compartment before flowing into the vehicle fuel tank.
See also Blending dispenser.