Gasoline Performance Rating

an index of the resistance to knock of gasolines used for aviation piston engines with spark ignition. The rating characterizes the power developed by an engine operating on a given gasoline relative to the engine’s power under identical conditions using isooctane standard gasoline, both in pure form (100-octane rating) and with various amounts of tetraethyl lead (an antiknock additive). The division of gasolines into grades depends on the octane number and, in the case of aviation gasolines, on the performance rating (seeGASOLINE).