The paper concerns the use of polymer additives for improving different characteristics of lubricants required in running of mechanical systems – especially tapered roller bearings. The macromolecular matter dispersed into the oil contribute to increase of lubricant film thickness and reduce the risk of damage by scuffing of the contacting surfaces.The purpose of this paper is to investigate the performances obtained in lubrication of concentrated contacts by using polyethylene as additives for the lubricant oil used for an four-high mill.