Here's a link with a few ideas to try:
How to Remove Oil Stains from Concrete
Check out one of my posts on removing oil stains from concrete: I did an (unpaid) review on 2 different products. This was not perfect but one of the products lessened the oil stain. It was a very old stain so maybe if you get it sooner than later it would do better:
Dry cement or cat litter.
Both need to be worked in with a wood block.
Sweep up after two days and re-apply if necessary.
sprinkle on cat litter to absorb. After a couple days sweep up and then use Dawn dish soap to help with any remaining stains
Start with oil dry to absorb all fluids. Then pressure wash with a degreasing solution.