Congratulations on the excellent MPG. There are several threads re: NMS tank capacity. IIRC, 18.5gal, but someone will correct me.
It's a bizarre, contorted tank shape, and the problem is getting the last 2 gallons in the tank. Veterans here advise a slightly uphill vehicle position (yes, it's counter-intuitive), as well as leaving the engine running (it's diesel, no fire risk). This seems to work for most. Of course, veterans also advise against challenging the fragile HPFP by running too low on fuel, as fuel temps increase. Also, of course, you don't want to run the tank dry.
The 2012s, maybe into 2013 production, the fuel gauge wouldn't ever show full, or if it did, would drop some as soon as the vehicle left the fuel station.
(Since I own 3 "e-turds", you might be interested to note: 2014 Avalon Hybrid, drove from Ft. Worth to Wash. DC, I30-I40-I81-I66, 75-80mph, fully loaded, through all the hills...2 tanks averaged 43mpg...and a whole lot less stink than your so-called "clean diesel." ...and careful: your diesel turd has significantly more stench than our E-turds
!)
FYI, my 2012 and 2014 NMS Passat TDIs averaged 44-46mpg for the same route, same ambient temps...)
((I'm sure several are wondering why I continue lurking, after bailing on our VWs. I'm fascinated by the CR technology, and the industry's attempt to clean it up. Also, the Toyota Hybrid forums are BORING!!!!...no dramatic threads of any kind...and very little excitement. Weeks pass w/o any posts...)