Bicarb is meant to be able to get it off too. It tells you on the box.

Good luck
Lol is there anything bicarb can't do?!?!

Can you just leave a car parked on top of the stain while they do the inspection? That way you don't have to panic too much if you can't get it off now, and can work on it over the next few months? We had some on our driveway, I think DF sprayed some degreaser on them and gave them a half-hearted hose and a scrub with a broom. I think they faded somewhat, but when we moved in there were oil stains there anyway so i don't think he worried about them too much! Lol