1. A colorless, flammable liquid hydrocarbon (C₈H₁₈) used as a reference standard in measuring the octane rating of gasoline.
Usage: chemistry; also called 2,2,4-trimethylpentane; technical term

Examples

• Isooctane is assigned an octane rating of 100 by definition.
• The fuel's octane number is determined by comparing its performance to a blend of isooctane and heptane.
• Chemists use isooctane as a standard reference compound in laboratory testing.
• Gasoline quality is measured against the isooctane scale.
• The engine knock resistance of the fuel was evaluated using isooctane as the benchmark.