After reading RICALI's post, I guess I need to retract?!?!....but I cant imagine using used oil .....even if filtered, very small particles will get through filter, and some of the particles consist of metal and minerals (road sand and metal from engine). I cant imagine that not hurting injection pump. But I can't say I really know for sure.

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)