You have prompted me to do a FAQ on this based on information gleaned from The Backroom forum at HJUK, as follows:- Biological washing powder, left to soak overnight, preferably after a warm day, then hosed off morning after. Washing powder soda crystals (used as above). Coca Cola, used as washing powder (used as above). Neat Fairy Liquid (used as above). Petrol, used as above (no naked lights). These products www.ocbp.co.uk/products4.asp The FAQ also covers getting oil off Tarmac drives.