[CWysong]

I have been doing research in adding an oil cooler to my SPORT PKG 335xi that did not come with one, for whatever reason...




This picture helps. Factory without an oil cooler does not allow the thermostat housing to be added, as you can see in the picture. You do need a new OEM oil filter housing that allows for the thermostat to be added. This is ~300 from Stett, I bet you can get it cheaper eslewhere.

If you have an OEM oil cooler, some kits come with a new thermostat that bolts to the special oil filter housing. But you DO need a new housing if you do not have a factory cooler. The oil filter housing w/ thermostat access is part 7 in the diagram above. Notice how the non oil cooled does not have that opening or mounting points on the filter housing.

Here is a DIY to upgrading the oil cooler from a non oil cooled engine. The first few picutres really show what is different on the oil filter housings.

http://www.e90post.com/forums/showthread.php?t=70021

[e90pilot]

I always thought that the part highlighted in yellow was just a distribution block. The stett oil cooler doesn't use that half of the housing. They have their own distribution block and a separate thermostat downstream.