The Corps of Engineers has historically used solvent-refined napthenic-type base oils (Group I) for lubricating hydroelectric turbines and associated governor systems. Products now being supplied by the lubrication industry for the same purpose are based on hydro-cracked paraffmic oils (Group II). While these Group II products are advertised to have superior properties for use in gas and steam turbines, they have been reported to result in foaming and sludge formation when used in hydroelectric turbines. A survey of Corps of Engineers hydropower facilities was conducted to determine the extent of such problems. In-service evaluations were conducted to more clearly define the problem. Purpose-designed oil filtration and warming devices were installed at one Corps powerhouse to determine whether foaming and sludge formation could be prevented when using Group II oils. Initial results were positive, and four modified filtration/warming systems were subsequently installed to compare performance and refine technical specifications for a recommended system. DISCLAIMER:The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.