NOTE 1 The carbon residue value serves as an approximation of the tendency of petroleum products to form carbonaceous deposits under similar degradation conditions, and may be useful in the assessment of relative carbon-forming tendencies of products within the same class. In this case, care should be taken in the interpretation of results.
For products which yield a residue in excess of 0,10 % (m/m), the test results are equivalent to those obtained by the Conradson carbon residue test (see ISO 6615) in the range of 0,10 (m/m) to 25,0 (m/m) (for details see Annex A).
This International Standard is also applicable to petroleum products which consist essentially of distillate material, and which may yield a carbon residue below 0,10 % (m/m). On such materials, a 10 % (V/V) distillation residue is prepared by the procedure described in 7.3.1 and 7.3.2 before analysis.
Both ash-forming constituents, as defined by ISO 6245 and non-volatile additives present in the sample add to the carbon residue value and are included in the total value reported.
NOTE 2 The presence of organic nitrates incorporated in certain distillate fuels will yield abnormally high values for the carbon residue. The presence of alkyl nitrate in the fuel may be detected by ISO 13759.