Any safe way to do black diesel?

Campbellsville, KY
Thread starter
I have several '80's Mercedes with the OM617 IDI diesel, and also run a shop so I have a steady supply of used motor/transmission oil.

I don't want to compromise the cars' injection systems but it would pay for itself to invest in equipment to filter and clean the waste oil if it can be run, even blended, safely. Common opinion seems to be that <5 micron filtering takes out the particles that would do substantial damage, which I'd probably accomplish with a centrifuge.

If I get the waste oil filtered to below 5 microns and free of water, etc., and blend it ~50/50 with pump diesel, will it still run a risk of shortening the life of the fuel system?
All the non-combustible adds in the oil will end up in your cylinders . Where will it go? Will it contribute to excessive wear? Will it clog an exhaust system? That is more what I would worry about. If all the fuel lines are metal and you pre-filter, I don't think the fuel delivery system will be that much affected.
I would give it a go as long as its relatively clean. They run cars off french fry grease from mickey D's. Some time ago i read they were using alcohol to absorb water and then settle out the paticulates in large drums. Then draw off the clean oil layer. Maybe process the oil then send a sample off for UOA to see whats left in it.