The Harvard filter is indeed from Evansville. It is a very high quality filter and is supposed to remove particles down to 1 micron.

I suspect that a lot of the older diesels use oil because the previous owners might not have been using a CH4 rated oil. When you switch to the proper oil the rings get cleaned and everything starts working as designed.
I don’t drive my 240D over 60 most of the time because I don’t like the sound of an engine spinning faster than a blender.