This page can be used to approximate octane values when blending pump gasoline with racing fuel to increase average octane. Those who need high octane fuels often do not need to run straight racing fuel, but rather a blend that is somewhere in-between racing fuel and pump gasoline. It is assumed that the octane obtained from mixing fuels will be the simple average of the two.

Your mileage may vary, and it probably will if you are the kind of person who blends your fuel.