Elastomer compatibility with fluids to which they will be exposed is one of the important determinants of elastomeric seal performance. Todays hot operating environments often require fluoroelastorners to provide the necessary seal life and reliability. However, there are diierences among fluoroelastomers (due to monomer composition) and among engine oils, transmission fluids and gear lubricants (due to additive and base stock variables). These differences can affect seal performance.Two fluoroelastomers containing tetrafluoroethylene (TFE) and propylene (P) in their structures have demonstrated better and more consistent resistance than FKM types of fluoroelastomers to a wide variety of engine oils, transmission fluids and gear lubricants. This paper demonstrates TFP/P based elastomers maintain their advantage under various time and temperature conditions.