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Principal formulation effects on oil-fluoroelastomer compatibility in European specification tests are reviewed, and detailed surface analysis of elastomer samples after exposure to oil reported. The mechanism of fluoroelastomer degradation has been investigated and found to be based on fluorine depletion of a thin surface layer by dispersant additives. Compatibility is determined by both the oil and the detailed composition of the elastomer. Correlations with field performance have not been published for current European elastomer tests. Failing oils have demonstrated satisfactory performance in field trials. Oil preageing affects seal compatibility, but probably differently for gasoline and diesel engine lubricants.

Analysis of oils from diesel engines historically has been limited to measurements of wear metals and changes in physical properties. This paper discusses the application of computer-assisted infrared spectroscopy in studying the chemical and physical changes of used diesel oils. A detailed study of various oils by this method reveals a variety of important information, including the fate of various additive chemistries and the decomposition products of the oil. Correlation of this technique with laboratory dynamometer tests and actual field service is discussed.