The used oil industry is complex and influenced by several factors which can vary significantly across the United States. Differences in the local industrial base, population and community demographics can affect the means and economics of used oil gathering, the quantity, quality and types of used oil collected and the markets into which the collected used oil is sold. Although some generalization can be applied to the industry as a whole, regional variations can influence the local effectiveness of any collection or treatment solutions adopted.

The used oil industry can generally be divided into five business segments:

• Generators who produce or generate used oil, typically through the replacement of oil that has been in service, with new oil;
• Gatherers / Collectors who collect and consolidate the used oil from the Generators and sell it to End Users;
• Consolidators / Blenders who further consolidate the used oil into larger quantities and either blend it with other oils to create blended fuel products or sell it directly to End Users;
• End Users who consume the used oil as a combustion fuel, use it to perform some beneficial service (typically other than that for which it was originally created), use it as a feedstock to create other valuable petroleum products, or re-refine it back into base oil;
• Brokers who act as middlemen and facilitate transactions between the parties listed above.

Some of the participants in the industry have operations that encompass two or more of these activities. For example, a Generator such as a steel mill, can also become an End User if they burn their used oil to help fuel steel making operations.