Being luxury car or not has nothing to do with which oil is recommended.
On your car I strongly recommend to use synthetic because of different reasons, one of them is having a turbo, which runs extremely hot and uses the engine oil. Synthetic oils resist heath on a higher level - also flows and lubricates a lot better in cold temperatures. The other thing is, these engines are bad to build up sludge, clogs breather valves. Good synth. oils has additives to prevent sludge build-up.
Use good synthetic, like Mobil 1 and replace it at no more than 5000 miles if you want to save money on the long term, otherwise you will replace turbo, breather valve, de-sludge engine, etc...
Zee