Previous articles in this series have dealt with the running-in of engines by Vauxhall Motors Ltd., and by The Daimler Co. Ltd. We shall include several other British motor manufacturers in this series, but in this article we describe the procedure adopted by Daimler-Benz A.G. and other German motor car companies for filtering and purifying running-in lubricating oil. This article is reporduced from ATZ, Automobiltechnische Zeitschrift, Stuttgart, by kind permission of the Editor, Prof. Dipl.-Ing. H. Buschmann.