There have been numerous schemes to re-refine used motor oil. The additives in fully formulatedmotor oil present a real problem vs refining crude oil. BP tried coprocessing used PCMO in a unit called a Coker that processes . It incorporates thin oils. The next time that unit shut down for widespread maintenance they found the small amount of PMCO in the unit feed had put twice the wear and tear on the equipment than prior operation without adding PMCO, and that ended that idea.
Safety Kleen has a small.process unit, small in comparison to a full crude oil refinery, dedicated to recycling used PMCO to recover the base stock. They're able to produce Group.II base oil to reformulated fresh PCMO. They get around a 50% to 60% yield for base stock.
The government is a huge customer for re-refined motor oil. Attempts to market re-refined PCMO at retail level has never been successful..Safety Kleen had quarts of oil on Walmart shelves back years ago, always priced at a disadvantage to freshly refined lubricant from crude oil. It didn't last long on those shelf spots. Valvoline went all out on their Next Gen PCMO made using re-refined base stock. They hyped up advertising on that product including sessions at colleges emphasizing the recycled aspect. It bombed again as pricing wasn't significantly less than conventional PMCO, and it only lasted a few years on the market.
Economy of scale for PCMO with base stock refined from fresh crude oil is less expensive to produce re-refined base stock PMCO.
Here's a web page with some videos aboutideo about the used oil collection and the re-refinerySafety Kleen re-refinery
https://www.safety-kleen.com/services
The other avenue to disposing used PMCO is to blend it with heavy oils that ships primarily use. It's limited to 3% in the mix to keep it from producing significantly extra wear and tear. This route doesn't do well with water or glycols in the mix.
We take our used PCMO to O'Reilly because they also accept used oil filters as well as used oil. I know they use Dafety Kleen because that's the name on the form you fill out to recycle our PCMO. With Safety Kleen these used oil filters are shredded with the metal going to scrap for recycling, and the non-metal.parts burned in a power plant designed to use this material.
If I have someting else like used ATF I take it to Aitozone as at least the stores I've used will accept this material. This leads me to believe Auto Zone's recyclers blends used PCMO & ATF all in the same tank at the store. Then I take the automatic transmission filters to a nearby Firestone with no hassle.
I've never recycled PCMO.and / or ATF at Advanced Auto because they've never been as nearby as an Autozone wherever I've lived.
The City of San Antonio offers free household hazardous waste material collections at no cost throughout the year. One of the items they accept is used PMCO. I've never used this because I want to dispose used PMCO, oil.flters, or used ATF shortly after I generate them. I don't like that material sitting around in the garage.