Combining the best of value and performance, Stens oil filters protect your engine from particles that could cause harmful deposits. The filter medium traps particles, keeping them from traveling with the oil throughout the system. To boost effectiveness, filter mediums are folded into pleats to increase the surface area for capturing particles. When indicated, Stens oil filters have pressure relief valves and anti-drain valves. Pressure relief valves open to allow oil to flow if the filter medium becomes too saturated. This valve protects the engine from oil starvation. An anti-drain valve prevents oil from emptying from the filter when the engine is off. This feature is important so that the engine receives sufficient oil when started. An anti-drain valve reduces engine wear that can occur due to insufficient lubrication on start up. On top of best-in-class performance, Stens oil filters are value priced to be easy on the budget compared with many competitive products. Most Stens oil filters are made in the USA.