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 D-524.