I'm from Greece. About 10 years ago, one of the two big oil companies (with their own refineries) named MOTOR OIL (What a fine name this is!) announced that they would invest over 200 million USD to modernize and expand their refining facilities with a vast recycling unit. I remember from the newspaper, that up to that year there was only one recycling unit so big in Texas and that the productivity factor would be 70%. 10 tons of used motor oil would give 7 tons of basic oil. I do not know about the use of the rest 30%.