Iso-octane

A hydrocarbon, C8H18, which has very high critical pressure and temperature. Iso-octane is used as the high reference for measuring the antidetonation characteristics of a fuel.

Aviation Maintenance Technician Handbook — Airframe, p. G-20

Also defined in 1 more source

An organic compound used as the high reference fuel for rating the antidetonation characteristics of aviation gasoline (CH3)2CHCH2C(CH3)3.

Aviation Maintenance Technician Handbook — Powerplant, p. G-16