This has already been mentioned in the 164/166 forum but its applicable to all cars.
http://news.bbc.co.uk/2/hi/business/8456116.stm
Follow the page down and open the spreadsheet , some useful info in that.
http://news.bbc.co.uk/2/hi/business/8456116.stm
Follow the page down and open the spreadsheet , some useful info in that.