AMSOIL SDF Filters are composed of a special cellulose, synthetic and glass blend media to provide longer life and improved efficiency. Performance tests demonstrated that AMSOIL SDF Filters provide up to 100 percent more capacity than other leading filters. They also achieve nearly 95 percent operating efficiency, outperforming all major brands. An oil pressure relief
valve assures proper oil flow at all times under all operating conditions. Each heavy-duty case has a drawn steel double-crimp at the base with rolledunder
seaming. An anti-drain back valve keeps dirty oil in the filter when engine is not running.