To recycle used oil, processors and refiners remove water, insolubles, dirt, heavy metals, nitrogen, chlorine, and oxygenated compounds from oil drained from automobiles or other machines. The resulting product-called “re-refined” oil-must meet the same stringent refining, compounding, and performance standards as virgin oil for use in automotive, heavy-duty diesel, and other internal combustion engines, and hydraulic fluids and gear oils. Extensive laboratory testing and field studies conclude that re-refined oil is equivalent to virgin oil-it passes all prescribed tests and, in some situations, even outperforms virgin oil.