This document specifies a test method for the determination of cetane numbers ( CN ) in diesel fuel, using a standard single cylinder, four-stroke cycle, indirect injection engine. The cetane number provides a measure of the ignition characteristics of diesel fuels in compression ignition engines. The cetane number is determined at constant speed in a compression ignition test engine equipped with a swirl chamber. The cetane number scale covers the range from zero to 100, but typical testing is performed in the range from about 40 CN to about 75 CN. The precision of this test method covers the range from 44 CN to about 66 CN. This document is applicable to distillate as well as paraffinic diesel fuels intended for use in diesel engines, including those containing fatty-acid methyl esters (FAME), ignition-improvers or other diesel fuel additives. When this engine test procedure is used for other fuels such as synthetics and vegetable oils, samples with fuel properties that interfere with the gravity-based pre-supply pressure to the fuel pump e.g. due to high viscosity can only be used to a limited extent. Precision data for such fuels are not available at this stage. NOTE 1 For the purpose of this document the expressions %(m/m) and %(V/V) are used to represent the mass faction and volume fraction respectively of a material. NOTE 2 The test method is also suitable for determining cetane numbers outside the range of the scope, however, the precision statement only applies for fuels in the specified range. WARNING The use of this standard can involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to take appropriate measures to ensure the safety and health of personnel prior to application of the standard, and fulfil statutory and regulatory requirements for this purpose.