While I understand that in some cases personal pride tends to inflate economy numbers, allow me to detail some facts and figures...
The car... 2014 TDI MT with 21k miles. Hankook directional snows on all four corners. Tires at 42 psi. Winter Front installed.
Weather conditions variable. Some considerable headwinds. Temps from the teens to upper 40's. No snow or slush. Winter blend fuel. Very little city driving but a good portion on secondary roads mixed with 70+ mph Interstate yesterday.
72 mile round trip eastbound and return from Elmira/Corning, NY Mostly flat terrain.
250 mile round trip westward on Rt. 17 over some rather steep terrain. 2200' at the highest point.
Yesterday to Orbisonia, PA via State College, Tyrone, and Huntingdon. Then return via cross country to Lewisburg and north on Rt. 15. If you know the areas described, or if you look at the map, you'll soon discover that the roads traveled are not conducive to stellar fuel economy. Further, I wasted no time.
From initial fill to the refuel last evening the car returned a calculated 51.9 mpg. I realize that there could be some variance in top-off but even a half gallon difference over the miles driven wouldn't make all that much difference. This car just loves to stretch its legs whether on an Interstate or on a narrow twisting mountain road.
I believe it fair to say that the Winter Front has a positive influence on performance. Full operating temp comes much sooner and the engine generally seems a bit happier overall. Normally I expect about a 10% hit with winter fuel and it would seem that allowing things under the hood to remain a bit warmer may help negate the impact of thinner fuel.
For those wishing to squeeze a bit better economy out of the TDI I would suggest "smooth" as the order of the day. Don't be afraid to move quickly or maintain Interstate speeds. Don't bother to do anything special, except to make every attempt to make your shifts seamless. As much as possible try for shifts at about 2000 rpm or just a bit more. Try not to retain the habits learned in back of a gasoline engine. Drive the TDI as a diesel should be driven and I believe a number of you will be greatly rewarded.