The use of ring type oil seals in modern turbo-compressors is a standard design procedure which has evolved as a result of experimental testing and field experience. Originally, major concerns were inner-seal leakage and losses associated with the fluid-film friction in the seal oil film. More recent applications of oil seals have been in compressors which run in excess of double the first shaft bending peak response speed. This fact has focused attention on the hydrodynamic characteristics of the oil seals. This paper presents a method of analyzing high-pressure ring type oil seals which enables the design engineer to determine the seals' influence on rotor-bearing stability. The results of the analysis are used in a multi-mass flexible rotor stability analysis to show how the oil seals can produce a zone of shaft-whip instability in high-speed turbo-compressors. Experimental results are presented which clearly indicate the presence of shaft whip instability before oil seal modifications and its total absence for the same conditions using an improved seal design.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Kansas City, Missouri, October 3–5, 1977