Re-refining Glossary

Base oils are components of many finished products,

including lubricating oils, automotive and diesel engine oils, lubricating greases, white mineral oils, rubber processing oils, industrial oils, and refrigeration and heat transfer fluids. Group I, II, III, and some Group V base oils are manufactured from various refining processes, including both crude oil refining and used oil re-refining.

Base Oil Group I

Group I base oils are the least refined among the three groups. Group I base oils are classified as less than 90 percent saturates, greater than 0.03 percent sulfur, and with a viscosity-index range of 80 to 120. Group I base oils are solvent-refined, which is a simpler refining process.

Base Oil Group II

Group II base oils undergo a more extensive refining process compared to Group I. Group II base oils are defined as being more than 90 percent saturates, less than 0.03 percent sulfur, and with a viscosity index of 80 to 120. They are often manufactured by hydrocracking, which is a more complex process than what is used for Group I base oils. They also have a clearer color and cost more in comparison to Group I base oils.

Base Oil Group III

Group III base oils represent the highest quality among the three groups. Group III base oils are greater than 90 percent saturates, less than 0.03 percent sulfur, and have a viscosity index above 120. These oils are refined even more than Group II base oils and generally are severely hydrocracked (higher pressure and heat). This longer process is designed to achieve a purer base oil.


means the gathering of waste, including the preliminary sorting and preliminary storage of waste for transport to a waste treatment facility.


means any operation which is not recovery even where the operation has as a secondary consequence the reclamation of substances or energy.

Extended producer responsibility scheme

means a set of measures taken by Member States to ensure that producers of products bear financial responsibility or financial and organisational responsibility for the management of the waste stage of a product’s life cycle.

Re-refining or regeneration

refers to any recycling operation whereby base oils can be produced by refining waste oils, in particular by removing the contaminants, the oxidation products, and the additives contained in such oils.

Separate collection

means the collection where a waste stream is kept separately by type and nature to facilitate a specific treatment.

Treatment to fuel oil

An energy recovery operation in which waste oil is processed to be used as fuel, which is the main alternative to re-refining waste oils into base oils.

Waste oil or used oil

refers to any mineral or synthetic lubrication or industrial oils that have become unfit for the use for which they were originally intended, such as waste combustion, engine oils and gearbox oils, lubricating oils, oils for turbines, and hydraulic oils.