What is the best way to remove old oil stains from concrete driveway?

I have always used kitty litter which you put on top of the stain and let sit for a day or so and then sweep up. It absorbs the oil.

Have you tried cat litter! It will absorb the oil. Then use a power washer in case any residue is left.

I would put some Dawn detergent on the oil stains, scrub it in, and let it sit a while. Then a hose set on "jet" to rinse, or one of those pavement sweeper water nozzles.

BLACK GROUT AROUND TUB?

Kitty litter will absorb the oil, let it set for a day or 2, then sweep up. If some still remains use blue dawn and scrub with a stiff brush followed by a power wash.