Running used motor oil, filtered or not, in your fuel tank in large quantities is not necessarily a good thing to do. At least not to a car you care about. I have a VW Dasher Diesel beater that I wouldn't think twice about feeding used/filtered oil as fuel, but I'd never put it in my MB. There are fine particles that you can't filter out, which don't do nice things to injection pumps and injectors at 2000psi. It's up to you, though. BTW, I think re-using the 9-hour Delo in your crankcase is fantastic!
