My understanding is that the anti-wear and anti-viscosity-breakdown additives are just as important as the base oil itself.

Time and heat break down these additives, which keep the oil working properly as a lubricant/coolant.

The reason my old Toyota Corolla got to 366,000 km and is still going is that I changed the oil regularly and without fail.

I wouldn't recycle oil in any vehicle I cared about, but in a long-term emergency cleaning/recycling would be better than doing nothing at all.