Two novel low-temperature ionic liquid processes are developed for the recovery of base oils from waste lubricant oils. One uses 3-(triethoxysilyl)-propylammonium-3-(triethoxysilyl)-propyl carbamate (TESAC), in which the waste lubricant base oil is insoluble, and the other uses trihexyl(tetradecyl)phosphonium chloride (P6,6,6,14Cl) in which the base oil is soluble. In the 3-aminopropyl-triethoxysilane (TESA)/TESAC process, waste oil components, including the base oil, are dissolved in the solvent TESA which is converted, in situ, with carbon dioxide to TESAC, recovering the base oil as an insoluble layer. In the P6,6,6,14Cl process, the base oil is separated from most additives as a solution in the ionic liquid from which it can be extracted with methanol. The recovered oils from both processes have properties consistent with lubricant oils in commercial use and the ionic liquids can be recovered for recycle minimising reagent use and providing a route to closed-loop base oil recovery and recycle.