I clean gas station islands that have diesel fuel that spills on the concrete. The concrete cleaners from your local hardware stores do not work. Is there anything that will take diesel fuel off easily?
At Home Depot you can get a product called Krud Kutter. It takes grease out of everything but I've never tried it on concrete. Painters use it for clean up and spills. You might try it - it's highly concentrated and I use if full strength all the time.
It's wonderful stuff. Someone once told me that Pert shampoo would take oil stains out of concrete as well.