Carbon Conradson residue is the percent of coked material
remaining after a sample of lubricating oil has been exposed to
high temperatures. Results are reported as a percentage of the
weight of the original sample. As far as the affect of residue on performance,
one opinion is that the type of carbon is of greater
importance than the quantity. Since compounded oils contain
metallic additives that generally leave a residue, other testing
should be done to also identify the type of residue rather than just
the amount. A weighed quantity of sample was placed in a crucible
and subjected to destructive distillation. The residue undergoes
cracking and coking reactions during a fixed period of severe heating.
At the end of the specified heating period, the test crucible
containing the carbonaceous residue was cooled in a desiccator
and weighed. The residue remaining is calculated as a percentage
of the original sample, and reported as Conradson carbon residue