No, it's not a turbo, it's the new gasoline-direct-injection engine.
Almost all new (european) cars use sythetic oil (turbo or not) mostly because of change intervals extended to 30-50 000km.
That seems to be a VWoA thing, over here the rating for the A4 1.8t was in the 1300-1500kg range, and yes of course it could be had with a trailer hitch from the factory. Back to your "box" trailer. How fast do you want to go with it? Assuming the 150HP turbo will have a v_max of about 220km/h, and considering that wind drag is proportional to the third power of the (air-)speed you would be able to go over 170km/h with a trailer that doubled the wind-drag compared to driving solo. Even with a trippled wind-drag you would still be able to run over 150km/h at full throttle. Do you really want to go that fast with a trailer?
Ingo