Under a contract from the Department of Defense (DoD), work was initiated by the Chemical Engineering Department of Auburn University to develop technology for converting waste oils into EPA specification grade fuel oil. DoD is particularly concerned with the development and utilization of this technology because it is one of the largest generators of waste oils in the U.S. A process objective was to dehydrate the waste oil, reduce its total ash content (< 0.1 wt %), and remove the impurities (such as sludge, carbon particles, acids, etc.) present in used oil. Particular emphasis was placed on demetallization and neutralization of waste oils by a chemical treatment. It was found from bench-scale studies that diammonium phosphate and triethanol amines were very effective in de-ashing, as well as in precipitating sludge and impurities from used oil. An extensive study was performed to determine the effect of various parameters on the ash and lead reduction of waste oil.