Precisely, hence I've never brimmed. 
Hey Gonz, if you don't brim a diesel how do you calculate the often fantastic fuel economy figures you've posted in the past.
Do you calculate or post from the trip computer?
For me the trip computer can be a bit optimistic.
Brimming, or to first click, anything that is done consistently from fill to fill. I just don't like brimming, and don't do it again once I've got my idea of an economy figure until circumstances change, such as living in a different city.