I have heard that baking soda paste will soak up most oils as it dries. Is there anything baking soda can't do?
Right on Steve! Remove a much of the oil you can. Then using detergent and baking soda, do not use soap, and scrub with a stiff brush and rinse well. Depending if the oil has soaked in for a long time, or if its baked in due to the heat of the sun. will determine if you will get most or all of the stain out.
I got a "right on" from the all-knowing Woodbridge. I feel like I have accomplished something today. Lori, he really knows what he's talking about, so I would heed his advice.
Detergent...soap? Laundry detergent vs. dish soap?
I goofed in my explanation to you. You want as Steve said. Ideally you should use sodium carbonate which is the primary chemical used in making detergents. Arm and Hammer makes it but its often hard to find. It's a lye and soda ash product. You can purchase this also at a pool supply store. Its strong stuff so be sure to wear gloves and eye protection and have a hose near by in case you get it on your skin.
Hope this clears this up for you.
Thanks, Woodbridge! Very clear now. I will see what I can locate locally.