importance of anti-drain back valve
Generally, the anti-drain back valve have the form of a rubber membrane adjoining the inner side of the can type filter cover. The membrane covers the holes where the contaminated oil gets through to the filter and protects from the back flow after the engine stops. The anti-drain back valve reduces the dry friction or mitigated solid friction time between working parts of the engine as protecting from the oil flow towards the pump and accelerates the oil flow into the working elements during the engine start, especially after a long break. The position the filter is screwed into the engine, conditions the valve application. If the filter works in the "cover up" position as shown in the picture below, the function of the valve is taken successfully by the gravitation. A valve is required when the filter in screwed in from the side or from the top of the engine body.