Differentiating between "waste oil" and "used oil"

The U.S. EPA defines the term "used oil" as any petroleum or synthetic oil that has been used, and as a result of such use is contaminated by physical or chemical properties. "Used oil" is a precise regulatory term. "Waste oil" is a more generic term for oil that has been contaminated with substances that may or may not be hazardous. Any oil contaminated with hazardous waste may itself be a hazardous waste, and if so, must be managed subject to hazardous waste management standards. Both used oil and waste oil require proper recycling or disposal to avoid creating an environmental problem.