Hope someone can answer this one which is baffling me ? Have replaced element oil fiilter in my daughters focus but can't figure out what the small plastic tab with the small o ring does ?? When you look into the filter housing the only place the element can fit is with the o ring and plastic tab restricting the smaller of the two pipes that come up from the housing. If the centre one of these two delivers the filtered oil to the engine what does the smaller one do ( which is effectively blocked by the filter element O ring as mentioned). The engine runs OK and no low pressure warning. Just can't figure it out ??

Any expaination would be appreciated.Ta