The content of used synthetic oils in the total amount of used lubricating oils has continuously increased. There are no information in literature about the re-refining of mixtures consisting of mineraloil basic and synthetic lub oils under hydrogenation conditions. Therefore a hydrogenation equipment in lab scale was created. The device is controled by a computer. Some analytical results of the hydrogenation of a polyolesteroil/polyalphaolefin-feed at a fixed catalyst are represented.