Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel

This standard test method specifies the procedures for determining the octane number of motor fuels designed for ignition engines. The approach involves comparing the performance of the test fuel against primary reference fuels under controlled operating conditions within a variable compression ratio engine. Measurements are taken to identify the point at which knocking occurs, allowing for the calculation of a numerical value that represents the fuel's anti-knock quality. The methodology ensures consistency across laboratories by defining specific equipment requirements, sample preparation techniques, and operational parameters. It is applicable to various hydrocarbon-based fuels used in spark-ignition internal combustion engines. The results obtained provide essential data for fuel specification compliance, engine design verification, and quality control in the production and distribution of motor fuels. This document outlines the necessary steps to ensure accurate and reproducible testing outcomes without prescribing specific fuel blends or engine modifications beyond the defined test protocol.