Hi Novice
This may help if you went to a pool shop and asked for a product called Zeolite. It may come as a different name. It comes in several forms eg. Powder, Grit or Granules and it is also used a pool filter medium. It is a natural occurring mineral that takes up oil grease heavy metals etc. Just spread it over the stains and leave it there for several days.
They use it in service stations to soak up oil and fuel spills.
Another option maybe Kitty Litter
http://www.cmzeolites.com.au/
I have friend that does sealing of concrete and stenciling. I wont see him until Sunday so I will ask him what is the best sealer and let you know next week if someone doesn't give you a heads up in the meantime.