For more severe oil-seal service at temperatures of 160°C (320°F) or higher for extended periods, more resistant fluoroelastomer compositions are required for long service life. High-fluorine VDF/PMVE/TFE elastomers, along with TFE/olefin FEPM elastomers, are much less susceptible to attack by oil additives. TFE/P fluoroelastomers have the requisite chemical resistance, but have low fluorine content, leading to relatively high swell and to soft vulcanizates with lower wear resistance than desired.