So my TDI vRS had its first service last week and the mpg recorded on the display is lower than previously. I used to get 50-52, now I'm down to 47 at the most. Obviously not a huge difference and real world it's unnoticeable. However, wtf?

I experienced the same thing when I had mine serviced in October. I thought it might have been the next tankfull after the service, its 1st tank of winter diesel or because it was getting colder but this could be an area 42 conspiracy. ?....