Here are two updated graphs. They look similar. But one is graphed by miles and the other by date. Note: how the mpg has dropped since cold weather set in.
I suspect this drop in mpg is due to 'winter diesel' having less energy / gallon. But it might also be because the 35d doesn't get up to optimum running temp as quickly. I'll probably never know, since BMW saw fit not to install a basic temp gauge in our 35d. I suspect BMW sees this omission as a 'safety feature', since a temp gauge might be too distracting and we'd be unable to keep our eyes on the iDrive screen where they belong.
Funf Dreisig
p.s. You can find the explanation of how I build these graphs and the very low mileage tankfuls in my previous posts in this thread.