Perfectly possible. A couple of years ago the winners of an eco run in Finland achieved 3.47 l/100 km - in a Volvo V70, and that was on what sounded like a very challenging route.
AMS managed a minimum fuel consumption of 4,6 l/100 km with the Passat BMT, their average was 6,9. 2,8 litre average? No way. 2,8 litre minimum? Maybe, but still hard to believe.
The whole story in detail: LINK: http://green.autoblog.com/photos/vw-passat-tdi-one-tank-drive/#photo-5008354/
Now we know the next hot-cakes on VW dealerships! I, however, smell something fishy... Publicity stunt?
Hmmm... Police officers oversaw the fill up and sealed the gas tank at the start of the trip. Add to that a photographer was on hand.... yeah, definitely a marketing exercise and not some John & Jane Doe writing in to VW to express their joy and amazement of their new VW. Duration of the drive was 3 days, didn't drive more than 14hrs a day and only in daylight..... just how slow were they driving for it to take a combined 3 days to travel 1,626 miles ?? Hypothetically, if they drove 10hrs per day for 3 days (so 30hrs driving time), that would equate to an average speed of 54 miles per hour. No doubt diesel power is the way to for the fuel-conscious. I'd love to buy one down the track.
^ Know you have my imagination working overtime. "VAG do you need a new record on fuel consumotion for a W16 engine in the Bugatti? Me and the wife will go @ 20km/h for 3 days, you provide the car!" Only way I'l ever get to drive a Veyron