I have also been trying to eradicate some oil spots on my garage floor left from the previous owner/builder. He parked his Harley in the garage while he was building the home. His scooter must have leaked badly as there are a few spots that are about 18" square. I have used Simple Green, Purple Power, gasoline, lacquer thinner, oven cleaner, Tide, brake cleaner, acetone, followed by oil dry, concrete, saw dust, etc.
As you can see I have tried many different cleaners to no avail! Any more suggestions? Oh, I also have a spot where he did a burn out with his H-D that lifted little pockets of concrete in a 4 square inch area too, along with leaving a 2' long black tire mark that I can not get remove either.
Yes, I know what you're thinking.... The guy must have been a real DA. Yes he was!!!! But he also was an outstanding craftsman.....
I don't want to apply epoxy because I fabricate with steel fairly often and the welder would make the floor look even worse!
Any suggestions you have will be appreciated.