hhmmm, let me think about that
1 - how bad can small particles of metal be to an engine??? that question immediately stops me from using used engine oil as fuel in my benz

2 - how bad can sub-micron particles of metal be for people breathing them in from the exhaust? that question immediately should stop you from using used engine oil as fuel in your benz. if you are looking for cheap/clean fuel then pick up some WVO and use that...