Just put 0.5 litre in my car (1st time in 5,000 miles) and thought I had maybe look at getting a 4 litre bottle or something to top up the smaller one that is in the boot. The stuff that came with it in the boot is: Castrol SLX Professional Powerflow Longlife III 5W-30. Can only seem to find it online in 1 litre bottles and would imagine buying 4 litres would be better value. Is it actually the same stuff as Castrol EDGE 5W-30 but just with a different label for Audi? Want to make sure I use the right stuff for the longlife servicing. Sorry if its a daft question, I'm not too knowledgeable when it comes to engines and all it gives me in the owners manual is a VW 507 00 which means nothing to me?