Have we forgotten that diesel fuel expands as it is warmed by the return fuel line, thus taking less fuel to fill the tank
. With a tank near empty or fueled the next day, not after a 130 mile drive, the fuel usage may be closer to 3.5 US gallons.
The best I've done with my 2.5 190D auto is 35mpg
(all freeway and tank near empty with summer fuel).