yaris 4D consumption

Hello everybody, for 3 weeks I have been driving the Yaris Diesel and would like to know how your consumption of the diesel is? The first three tank fillings have consumed the car with moderate driving between 4.5 and 4.8 liters. On the weekend I made a tour of 400 km with the cars occupied by four people. Speed so 120-140, running air conditioning and about 1 hour traffic jam. There the Yaris swallowed 5.8 l diesel. Well, it seems a lot to me. So just over five would have been o k found. Regardless of this tour I thought that I could drive the car just below the indicated 4.5 liters. The seller said the consumption would be the first 5-6tsd kilometers like with tightened handbrake. Is that so? wynton