Interesting! I've never looked closely at the oil circuit and just took a look at FSM 18-005 Oil circuit, oil pressure, pressure relief valve and oil filter. Pretty sophiscated oil filter!

From the diagram and description, it does appear that if the oil cooler is blocked or bypassed (note the oil cooler is essentially blocked by the thermostat with a cold engine), the engine will still get filtered oil via the main flow filter component (24a), which is separated by a seal to the bypass filter component (24).

Up until now, I didn't know there are 2 separate filter components in the filter element. I'm gonna have to cut one open to have a closer look and see how it is constructed.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked