ASTM D189 Conradson Carbon Residue of Petroleum Products
This method is intended to measure the coke-forming propensity of oils under extreme temperatures causing cracking and pyrolysis. The sample is placed in a crucible and heated to evaporate and reduce the material to a coke-residue or 'carbon residue'. Ash-forming additives can give an erroneous indication of coke-forming tendencies by adding to the weight of residue formed. Carbon residue is a useful guide in the manufacture of base oils and finished lubricants. Results differ from those obtained by ASTM D524.