I have a question about oil filters, when you look at an oil filter (wix for instance), underneath the holes where the oil enters/exits the filter there is a red colored material that sits right up against the holes, appears to be a rubber substance, anyways does the oil have to drain through this material?
oil filter question
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This is the backflow preventer. The direction the oil flows in forces the flap open during operation. When the engine is shut off it prevents the oil in the upper passages from leaking down through the filter. Incidentally some cars are built with filters that do not have this valve due to the fact that they are filled on the assembly line from the upper passages in a few seconds. When replacing the factory filter though a valved filter should be used in most cases. RW
It's a one-way anti-drainback valve. Oil doesn't really pass through, but around. The pressure of the oil contained in the filter after engine shutdown pushs against it from the inside and allows it to seal.
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