The problem is soot in used oil, which I am not sure you can filter out to nil, which means scoring and scratching of the engine internals. I don't know that anyone can predict the impact on longevity, but why change your oil if you don't worry about those soot particles?

In an emergency, motor oil, cooking oil, fresh tho. I had to change a fuel filter at a friend's house, no oil to fill the filter, used corn oil. Everyone got a kick out of that!

I like the idea (vaguely) seems like better disposal, the reality is more pollutants end up coming out the exhaust, if only more soot. I am trying to get to 500K on mine.

Could be wrong, maybe I have as much soot in there even as I write this. Anybody done soot level analysis? Ok, ok, checking the archives.....

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K