Synthetic esteroils are important base oil components for automotive lubricants. The content of used synthetic esteroils in the total amount of used lube oils has continuously increased. No information was found in the literature about the behaviour of synthetic esteroils under hydrogenation conditions. Therefore the hydrogenation of a polyolesteroil in mixture with a poly-alpha-olefin was investigated. The products were characterized by gaschromatography mass spectrometry.