A literature search to identify deleterious effects of using re-refined oil did not disclose any validated occurrences. Significant engine testing using re-refined lubricating oil is reported and no cases were discovered in which engine operation was affected negatively by the use of re-refined oil. The American Petroleum Institute (API) allows the use of re-refined base stock oils in the blending of end use lubricants.
Based on oil sample testing performed in this research as well as other authoritative sources, it was determined that no significant chemical or physical differences exist between re-refined and virgin oils. Differences noted in this research were related to higher levels of poly-nuclear aromatics (PNA's) in the re-refined oil. PNA's are formed due to the extreme conditions of temperature and pressure during operation of an internal combustion engine. PNA components are essentially removed by the hydrogenation process during re-refining and the trace amounts detected in new re-refined oil do not affect the oil's physical performance characteristics. Similar levels of PNA's were detected in used re-refined and used virgin oil, thereby indicating that the chemical change during use in an internal combustion engine is independent of the oil used.
Lubricating fluid logistics and handling procedures were studied and recommendations related to the screening of suppliers and the use of purchasing specifications to insure the procurement of only qualified supplier's products are presented. Purchasing specifications are generally acceptable but specific requirements must be stringently enforced to ensure that only quality lubricating products are purchased.
Alternative contracting arrangements that offer lubricating fluid procurement and disposal cost savings are suggested. Suppliers have indicated interest in determining cost-effective approachs for supplying lubricants and collecting/disposing of used fluids. Although this research was performed for the Texas Department of Transportation (TxDOT) the recommendations presented are appropriate for other vehicle fleet operators.