
xiii
Preface
Used lubricating oil is a valuable resource. However, during service, lubricating oil
becomes contaminated by a number of additional components (from engine wear)
such as iron and steel particles, copper, lead, zinc, barium and cadmium (two highly
toxic metals), sulfur, water, and dirt. In addition, the organic constituents of lubri-
cating oil will also undergo changes in use and produce undesirable contaminants.
Because of these contaminants, disposal of used lubricating oil can be more environ-
mentally damaging than crude oil pollution.
Thus, lubricating oil becomes unt for further use for two main reasons: accumu-
lation of co