yeah your right there, petrol also the best to remove engine oil stains from concrete drive way or concrete floorBelieve me, Petrol is awesome at removing underseal or any bitumen based product. Its no good putting on a cloth and wiping as all your'e doing is removing the surface. It needs to penetrate and then it will just lift away.
If you have heavy deposits scrape it first with a plastic scraper then remove the remainder with petrol.