That's incredible - they drove at about 65 kilometers per hour and that's not a traffic jam where hybrid cars show themselves well, so "hybrid" alone doesn't explain how it was possible.
For comparison: I know an owner of a Ford Focus C-Max with 2 liters gazoline engine and they report fuel consumption of about 14 liters per 100 kilometers. I agree that comparing gas versus diesel is not completely fair, but still 3 liters versus 14 liters looks impressive.
This story is widely discussed and some people say the car was "tuned".
I wonder what tuning that might be? How is 100 kilometers on 3 liters of fuel on a 1,6 liters car possible?