ASTM D2699-15a
Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel

Standard No.

ASTM D2699-15a

Release Date

2015

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM D2699-16

Latest

ASTM D2699-24

Scope

5.1 Research O.N. correlates with commercial automotive spark-ignition engine antiknock performance under mild conditions of operation.

5.2 Research 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-O.N. determinations.

5.2.2 Research O.N., in conjunction with Motor 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 U.S., and is referred to in vehicle manuals.

This is more commonly presented as:

5.2.3 Research O.N. is also used either alone or in conjunction with other factors to define the Road O.N. capabilities of spark-ignition engine fuels for vehicles operating in areas of the world other than the United States.

5.3 Research O.N. is used for measuring the antiknock performance of spark-ignition engine fuels that contain oxygenates.

5.4 Research O.N. is important in relation to the specifications for spark-ignition engine fuels used in stationary and other nonautomotive engine applications.

1.1 This laboratory test method covers the quantitative determination of the knock rating of liquid spark-ignition engine fuel in terms of Research O.N., 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 using a standardized single cylinder, four-stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions. The O.N. scale is defined by the volumetric composition of PRF blends. The sample fuel knock intensity is compared to that of one or more PRF blends. The O.N. of the PRF blend that matches the K.I. of the sample fuel establishes the Research O.N.