Yes, in the context of a 15 year old, 6 cylinder, it's about right. The 2.8 / 2.8 VW VR6 engine was about as economical on a run too. So it's only about the same as similar examples.
It was credibly more efficient than competing similar configuration engines. The V6 in the Mondeo ST for example was always noticeably more thirsty.
The F10 is also heavier than the E39 though. That's like carrying 2 fat guys like me around everywhere.
530i E39 - Curb Weight (MT) : 1540kg
530d F10 - Curb weight 1720 kg
My 530i is 1605kg, no idea where that 1540 comes from. It's only 100kg lighter.