Harold & Susan Vordos wrote:

Make sure you have no oil spots on the concrete. If you do, they can be
removed totally by soaking the spots in solvent (Stoddard, or mineral
spirits) and then covering the spot completely with kitty litter (Oil-Dri),
which should then be soaked with solvent. Let the entire mess dry
naturally. The evaporation of the solvent liquefies the oil and draws it
out as the solvent evaporates. You can clean even old, heavily soaked spots
that way, although it may take two attempts. Works great, and no hard work.

Works very well but I save the sawdust from my tablesaw and beltsander.
I found that this works as well as kitty litter and is free. :-)

Ted