The
oil will not flow through the filter in reverse. Normally the
oil flows out of the pump/block into the outer perimeter slots, into the filter canister through the filter media towards the center of the canister and then out the hole in the center of the filter and into the main
oil galleys to be distributed throughout the engine. The silicone rubber flapper valve that lies behind each of the slots is specifically designed to prevent oil from flowing in reverse.