Good People, A colleague asked if I could help him do an oil change on his A150 petrol. Well I unscrewed the oil filter top, removed the element to be greeted with a small 'top hat' plastic plug which was inside the element effectively blocking off the top end. The whole assembly then sits on a spigot which is spring loaded, and compresses down when the top is screwed back on. Anyone else come across this arrangement ? Many Thanks in advance.