Yes, I know that having a car is unsustainable, but nevertheless I'm interested in the most sustainable way to remove an oil stain from my driveway.
Unsustainable suggestions I've had include using kitty litter (mining bentonite is hardly sustainable), and chemical degreasers (probably petroleum based).
Obviously used oil from a car is pretty toxic, so there's probably no avoiding sending the material I use to soak up the oil to landfill (unless perhaps it's safe to burn in small quantities in a hot fire, depending on what material I soak it up into?). However using a material that has the lowest possible environmental impact is something I can control.