A 0w30, 5w30 or 10w30 oil can replace any oil requirement for straight 30w, long as they're diesel rated.
For my money I'd go with a 0w30 if I could find it. So far, I haven't found such for a diesel. My VW TDI uses a special 507 C3 oil made by Castrol that's 5w30. You can buy it at a VW dealership.
Ralph
We've got some 0W40's up here.... Mobil might meet your VW spec, possibly Castrol. Can't say I've seen a 0W30 yet.
Bought some Amsoil OE 10W30 this week, to run in my 7.3 this winter.
Rgds, D.