1.1 This method is intended for determining, under prescribed conditions, the amount of carbon residue left after evaporation and pyrolysis of non-volatile petroleum products which partially decompose on distillation at atmospheric pressure.
Note — Petroleum products containing ash-forming constituents as determined in accordance with P : 4 of IS : 1448* will have an erroneously high carbon residue depend-ing upon the amount of ash formed.
1.2 In diesel fuels, the presence of amyl nitrate causes erroneously high values. Accordingly, this method is applicable only to base fuels without this additive.
1.3 This test indicates the relative coke-forming propensity of petroleum oils.