The present invention relates to a polymer thickener for lubricant grease compositions, wherein the thickener comprises a mixture of (1) a high molecular weight (co- or homo-)polymer of propylene with a weight average molecular weight .gtoreq.200,000 and (2) a low molecular weight (co- or homo-)polymer of propylene with a weight average molecular weight .ltoreq.100,000. The invention further relates to a lubricating grease composition comprising a lubricating oil and the above polymeric thickener, as well as a method for preparing said grease composition. Also, the invention relates to the use of such a polymer thickener in the preparation of lubricating grease compositions with improved oil bleeding characteristics at low temperature and improved noise characteristics and/or improved mechanical stability.