Look on e-bay, and type in "biodiesel"
You will have the opportunity to bid on a process to convert used engine oil into "diesel" fuel.
I think it's about $100US, and I've posted a couple of times.
I contacted the seller, and asked what the viscosity was..."similar to diesel", with no further comment.
It can be clarified, but not cracked to a thinner viscosity without a refinery.