O.K....
I am not suggesting anyone else try this, so I am not responsible if someone blows himself or herself up, even though that shouldn't happen doing this.
We are professionals; don't try this at home...
One day I had to get up some oil stains from a couple of garages, failure wasn't an option. The super said I had to get it up and I didn't get any help or valid suggestion when I asked so I made up a cocktail of chems because everything else failed.
I took mineral sprits, turpentine, citric acid, and some brown powder from Delco, some yellow powder from Delco, and water to get the citric and powders to activate. I shook them for around 2-minutes until they were basically as one. I applied it to the oil stains expecting nothing.
I let it sit for about 5-minutes, scubing it a couple of times and then with the hottest water I could get from the pressure washer, rinsed it off as well as I could.
Boom!! It was gone!! Dried the exact same color as the cement.
I tried to subtract a chemical here and there to see which one was really doing the work, but every time I did, it wouldn't work.
I never got called back and the super was really satisfied with the results.
Oil being a petroleum product and using other petroleum products to fight it was probably what lifted it, the soap dissolving the lifted matter and I guess the acid doing its thing all worked hand and hand; who really knows, I was just happy to get the heck out of there before it came back.