Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel
1Key Takeaways
5.1 Motor O.N. correlates with commercial automotive spark-ignition engine antiknock performance under severe conditions of operation. 5.2 Motor O.N. is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to the matching of fuels…
2Scope / Description
5.1 Motor O.N. correlates with commercial automotive spark-ignition engine antiknock performance under severe conditions of operation.
5.2 Motor O.N. is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to the matching of fuels and engines.
5.2.1 Empirical correlations that permit calculation of automotive antiknock performance are based on the general equation:
Values of k1, k2, and k3 vary with vehicles and vehicle populations and are based on road-octane number determinations.
5.2.2 Motor O.N., in conjunction with Research O.N., defines the antiknock index of automotive spark-ignition engine fuels, in accordance with Specification D4814. The antiknock index of a fuel approximates the road octane ratings for many vehicles, is posted on retail dispensing pumps in the United States, and is referred to in vehicle manuals.
This is more commonly presented as:
5.3 Motor O.N. is used for measuring the antiknock performance of spark-ignition engine fuels that contain oxygenates.
5.4 Motor O.N. is important in relation to the specifications for spark-ignition engine fuels used in stationary and other nonautomotive engine applications.
5.5 Motor O.N. is utilized to determine, by correlation equation, the Aviation method O.N. or performance number (lean-mixture aviation rating) of aviation spark-ignition engine fuel.6
1.1 This laboratory test method covers the quantitative determination of the knock rating of liquid spark-ignition engine fuel in terms of Motor octane number, including fuels that contain up to 258201;% v/v of ethanol. However, this test method may not be applicable to fuel and fuel components that are primarily oxygenates.2 The sample fuel is tested in a standardized single cylinder, four-stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions. The octane number scale is defined by the volumetric composition of primary reference fuel blends. The sample fuel knock intensity is compared to that of one or more primary reference fuel blends. The octane number of the primary refer......