1.1 The purpose of this standard is to indicate the method used to determine the detonating characteristics of gasolines used in spark-ignition automobile and aviation engines(1). 1.2 The characteristics of automotive gasoline are expressed as Motor Octane Index (IOM)(2). 1.3 The characteristics of aviation gasoline are expressed as Aviation Method Octane index below 100 and as Aviation Method Detonation Resistance index (Performance index) above 100. (See standard UNE 51-006/2 ).