I carry out my own maintainence on my cars and have recently bought an a4 avant tdi 2.5. Service isnt due yet but want to cahnge the oil and filter for peace of mind.See that you can use either 5w30 or 5w40 fully synthetic on euro car parts. Which do you recommend? Does it really matter if you buy the quantam long life oil? I have a dingbro account and can get comma oil cheaper than any shop,my girl also has a tdi golf which im sure uses the same oil so it would be benificial to get a 25 litre drum so i could use it to service and top up both. Any info is much appreciated. Thanks in advance.