Bluetec.

We was in a road together and we said to restart the consume of the car in a certain moment and after we restarted the fuel consumption we cruised at 80 km/h the I6 was 5.8 and V6 bluetec 6.2. I6 MY is 2003 and Bluetec 2008, but idont belive the I6 fuel consumption, he said that in a moment it was 5.0 and after a small acceleration it was directly after 2 sec 6.0 how is that possibile, also when I6 its in downhill the fuel consumption it is so ****ing low lower than 5.0 and when it is in a uphill it increase like crazy 10-12 l/100km, WTF is this