My four year old concrete garage floor has now seen the restoration of the bird, and has the odd bits of oil and god knows what on it. I spent most of the weekend cleaning it out and moving stuff to a storage garage I rented, so I can epoxy the floor. I am going to start with muriatic acid, scrub it in with my trusty boat brush, and then pressure wash it.

Is there not some sort of enzyme based oil eating product out there? It may help in your case. I'll let you know though how the muratic acid works...I just happen to have a 5 gallon pail of it left over from doing the exposed agg driveway before I sealed it.

Not cheap, but they do have that rubber garage floor matting.....that would work well!