Used lubricating oil is a valuable resource, but it can be an environmental problem and a financial liability if improperly disposed of. Used oils pose hazards to human health and the environment, and therefore need to be managed safely. The mismanagement of used oil can contaminate air, water and soil. The objective of this work is to investigate the re-refining of used lubricating oils using solvent extraction process. The characteristics of used lubricating oils, utilization methods, elimination methods, environmental and human health effects were reviewed. Also, the various re-refining...