Think about waste motor oil for a minute. You take it out of your engine so it won't damage mechanical clearances of several thousandths of an inch, take out the 'chunks', and run it through an injector pump with clearances in the ten-thousandths? Does that bother anyone else??
IMHO only a centrifuge (or expensive few-micron filter) will clean WMO enough to reuse it for fuel. Either of those methods cost a lot to set up, fitlter cost, and time to manage. My Diesels get the best fuel I can find from the busiest stations, with Power Service additive. My used motor oil gets re-refined by the big boys.
YMMV of course
tennmogger