That's quite the MPG to pull off... I have been able to squeeze as much as 78.5 mpg (1114.7 mi on 14.201 usg) from a tank in my 1991 GTI TDI, bit it's got manual steering, no A/C, 2,420lb empty weight, .34 Cd and 20.559 sq-ft frontal area. In order to get that I had to drive mostly 1200rpm in 5th gear (about 35-40mph). I didn't have temperature in my favor though. This was done entirely with 15-30 mile trips starting cold every time over a month. I can't imagine what they did to average over 80 on a common rail Passat...
