I have to say Vpower diesel is more than placebo. With milage I do I got to test the lot. Found on both my cars e46 and E90 that with BP standard or ultimate car run pants. When I moved to either Shell standard or Sainsubyry Diesel I got very good performance. Move to Vpower and the car was noticibly more eager to pull.
Recently been running esso and car has felt crap even with new Performance Pack it just felt rough. Been running the tank down and will be going over to shell asap.
The biggest difference is when you get to europe their have slightly differnet quality diesel and in past found normal shell there give snearly same car feedback as Vpower here. Fill up with VPOWER in germany and its like having a remap