A compression stress relaxation test method consistent with ISO 3384 is being used for the evaluation of sealant materials. The test measures important material performance characteristics not measured by traditional test methods. This paper provides a brief introduction to compression stress relaxation. This is followed by a discussion of the effects on gasketing materials, particularly when the gasket is confined to a groove, of engine oil contaminated with gasoline. The paper concludes with a discussion of using compression stress relaxation to design improved materials for automatic transmission fluid gaskets. In all cases silicone rubber is the primary material being studied.