I see from other posts your having fun the the on board computer milage/fuel consumption.
My old 440 TDI which had a dodgy fuel guage, just managed 480miles on a tank which I remember as being 50 liters, and that was travelling at speeds beyond "optimal fuel consumption".
General when I filled up and zero'd the trip, I could predict how much fuel I was going to have to purchase next time my diving the trip by ten.
The fuel guage was so flaky that general principle was "refill between 400 and 500 miles"
I've just put 60 litres in the V70 TDI , I've no idea what it will do, however my father claims 600 miles on trips to the south of France.
I miss the acceleration on a petrol engine, but I don't miss the fuel bills.
Barmy