The "ECO" anti-siphon valve protects from oil flow from the filter after the engine stops. Therefore its function is similar to the anti-drain back valve. The only difference is that the "ECO" valve is placed on the "clean side" of the filter. As a result of installing both valves, the filter is always filled with oil, no matter if the engine works or not. It shortens the dry or mitigated solid friction between working parts of engine during start as the oil flow gets into the engine quicker. This effect, commonly called "dry start" causes serious abrasive wear and therefore it is important to shorten its length. Moreover "ECO" valve efficiently protects from oil outflow from filter during replacement. Hence protects the environment from the used oil spilling.