ASTM D2700 - 13b

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

    Active Standard ASTM D2700 | Developed by Subcommittee: D02.01

    Book of Standards Volume: 05.05


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    Significance and Use

    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:

    Equation D2700-13B_1

    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.

    Equation D2700-13B_2

    This is more commonly presented as:

    Equation D2700-13B_3

    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. Scope

    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 25 % 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 reference fuel blend that matches the knock intensity of the sample fuel establishes the Motor octane number.

    1.2 The octane number scale covers the range from 0 to 120 octane number, but this test method has a working range from 40 to 120 octane number. Typical commercial fuels produced for automotive spark-ignition engines rate in the 80 to 90 Motor octane number range. Typical commercial fuels produced for aviation spark-ignition engines rate in the 98 to 102 Motor octane number range. Testing of gasoline blend stocks or other process stream materials can produce ratings at various levels throughout the Motor octane number range.

    1.3 The values of operating conditions are stated in SI units and are considered standard. The values in parentheses are the historical inch-pounds units. The standardized CFR engine measurements continue to be in inch-pound units only because of the extensive and expensive tooling that has been created for this equipment.

    1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For more specific hazard statements, see Section 8, 13.4.1, 14.5.1, 15.6.1, Annex A1, A2.2.3.1, A2.2.3.3(6) and (9), A2.3.5, X3.3.7, X4.2.3.1, X4.3.4.1, X4.3.9.3, X4.3.12.4, and X4.5.1.8.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ANSI Standard

    C-39.1 Requirements for Electrical Analog Indicating Instruments

    Energy Institute Standard

    IP224/02 Determination of Low Lead Content of Light Petroleum Distillates by Dithizone Extraction and Colorimetric Method Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR, U.K., http://www.energyinst.org.uk.

    ASTM Standards

    D1193 Specification for Reagent Water

    D2268 Test Method for Analysis of High-Purity n-Heptane and Isooctane by Capillary Gas Chromatography

    D2360 Test Method for Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas Chromatography

    D2699 Test Method for Research Octane Number of Spark-Ignition Engine Fuel

    D2885 Test Method for Determination of Octane Number of Spark-Ignition Engine Fuels by On-Line Direct Comparison Technique

    D3703 Test Method for Hydroperoxide Number of Aviation Turbine Fuels, Gasoline and Diesel Fuels

    D4057 Practice for Manual Sampling of Petroleum and Petroleum Products

    D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants

    D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products

    D4814 Specification for Automotive Spark-Ignition Engine Fuel

    D5842 Practice for Sampling and Handling of Fuels for Volatility Measurement

    D6304 Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration

    E344 Terminology Relating to Thermometry and Hydrometry

    E456 Terminology Relating to Quality and Statistics

    E542 Practice for Calibration of Laboratory Volumetric Apparatus

    E1064 Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration


    ICS Code

    ICS Number Code 75.160.20 (Liquid fuels)

    UNSPSC Code

    UNSPSC Code 15101506(Gasoline or Petrol)


    DOI: 10.1520/D2700

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