I have spent 20mins looking for this post somewhere else, but cannot find even though the search engine brings back 237 results!!

Which oilis better for my 2.5 V6 TDi?

would it be the 0-30w Castrol Edge (that the dealer recommends)

OR

0-40w Mobil oil do?

What is the main difference in 10W? Both oils are fully synthetic. just not sure which to buy!

cheers