There are long-established arguments for recycling motor oil. The underlying theory is that natural oil consists of a collection of molecules of varying nature and quality. Service in an engine causes a kind of Darwinian "survival of the fittest", so by the time the oil is changed, many of the weakest have broken down, whether due to time/temperature, or pressure. Hence if the reclaimed oil were processed as well as virgin oil is, then had the same additives provided, it would be the better of the two products. Essentially, this is rather similar to the arguments for synthetic oil: it is made up of molecules all formed under similar, chosen conditions, and therefore they should be more uniform and suited to their task.
Historically the problem has been that reclaimed oil was not processed nearly as well as virgin oil, and did not receive the same additives.
