My 250SE Cabriolet had a feature I was not aware of. Underneath the injection pump is an oil/coolant heat exchanger. This was also an option on late 230SLs. Instead of a separate cooler that the M130 engined cars have, the heat exchanger helps warm up the oil when the engine is cool and cool it down when the engine is hot.
There are lines from the oil filter housing that go to the heat exchanger, as well as coolant lines that come from the side of the block. An example is pictured below. The picture is not my heat exchanger. […]
