In alt.home.repair, on Wed, 11 Nov 2020 08:48:29 -0500, major
wrote:

Had a recent motor oil quart slowly leek onto a ribbed concrete surface.
Not all of it leaked, but it left a slick about 2 feet in diameter. I
have tried to clean it up with materials I had on hand, mainly absorbing
as much as I could with potting soil and sand, then scrubbing the
remainder with Dawn dishwashing liquid solution,

I don't know much about Dawn, except they recommend it for grease, and
it must be different from other "soaps" because when I've used it, it
makes all the cuts on my hands sting, and nothing else ever did that.

paper towels dipped
into that, and then I would scrub. Looks like I got most of it, but I
still see some remaining. Best way to remove that would be welcome.
Thanks.

A wire brush? Long enough to get to those ribs. Well, any brush is
long enough for that. Maybe thin enough to get into little crevices? I
got a stain on some non-smooth fabric seat cushion, and the fingernail
brush with plastic bristles, with soap, didn't get it all clean. Next
planned step is a brush with thin metal bristles for suede. I don't
know if it will work.