Used oil re-refining is the process of recovery & restoring used oil to new oil by removing chemical impurities, heavy metals and dirt at re-refineries. Vacuum Distillation is the core process for a facility capable of producing re-refined base-oils to virgin base-oil quality. In vacuum distillation the feedstock can be separated into products of similar boiling range to better control the physical properties of the lube base stock "distillate cuts" that will be produced from the vacuum tower products. The major properties that are controlled by vacuum distillation are viscosity, flash point and carbon residue. The material that emerges from the vacuum distillation process has many of the properties of lube oil, but it still includes some contaminants. The lube oil coming out of distillation unit is further processed using Hydro treating technology the removal of contaminants takes place by exposing the oil to hydrogen gas, at very high pressure and temperature, in the presence of a catalyst. The catalyst promotes chemical reactions that remove trace metals and other contaminants from the lube oil.