Also known as: lubes
Base oils are not a fuel. They are blendstocks used to formulate a variety of lubricating oils for use in engines and other machinery.
Base oils are produced by extracting and treating high-viscosity material from narrow distillation cuts of vacuum gasoil or vacuum resid. This requires special processing through a number of different units comprising the lubes plant.
Producing base oil is typically very profitable for a refinery, because it allows the refiner to take some of the lowest valued part of crude oil, vacuum gasoil, or vacuum resid, and sell it as a high-valued specialty product. However, base oil production facilities have a relatively high capital cost per barrel, so only a subset of refiners have installed them.