While hydropower plant efficiency is exceptional, very little has been done to further improve its already high level of efficiency. In this regard, the bearings stand out as one of the major sources of losses in the plant that has potential for significant improvements with relatively little investment. One way to reduce losses while maintaining operating characteristics is to change lubricating oil to a higher viscosity index (VI) lubricant with a lower viscosity base oil. Studies showed that the thermal performance of mineral-based oils could be improved through the use of VI improvers to match that of synthetic lubricants. Another study investigated the case of polyalphaolefin-based lubricants, which found that lubricant with high VI provides performance equivalent to higher viscosity lubricants with lower VI ratings. Environmentally adapted lubricants, because of their inherent higher VI, provided higher viscosity in the region of lowest film thickness and lower viscosity in the rest of the bearing than standard mineral oil-based lubricants. This reduction in viscosity throughout the bearing led to a measurable reduction in power losses in the bearing system while maintaining desirable film thickness. Lubricants studied in this testing include industry standard VG32 mineral based turbine oil as a reference and synthetic ester and mineral based lubricants enhanced with polymer based VI improver additives. This is an abstract of a paper presented at the 2009 World Tribology Congress (Kyoto, Japan 9/6-11/2009).