I have a 320d, that i drive fairly hard, and i get consumption of about 8.2l/100km to 8.5l/100km.
It all depends on how you drive, ride the clutch, take off, brake and so on.
consumption is determined largely by driving style. you will find that on a long run, the diesel is frighteningly frugal, but on spirited driving in traffic, it still beats the petrols, fuel wise that is.
Also, check if you are filling 500ppm of 50ppm, i have heard that 50ppm gives you much better consumption as compared to 500ppm, but have not ready any scientifically based studies that can proves this, so at the moment it is all conjecture.
any way, thats my 2c worth.