I've been perusing the new Audi A4 online recently, and noticed the fuel consumption figures for the 2.0 TDI models are pretty impressive, the CO2 is good also:

 

2.0 TDI ultra 150 : 74.3 mpg / 99 g/km

2.0 TDI ultra 190 : 72.4 mpg / 102 g/km

2.0 TDI 150 : 70.6 mpg / 106 g/km

2.0 TDI 190 : 64.2 mpg / 113 g/km

2.0 TDI 190 quattro : 64.2 mpg / 114 g/km

 

 

Then i spotted the reason why this could be:

 

• Fuel tank 40 litres - standard on 2.0 TDI models but can be upgraded at no cost to 54 litres
• AdBlue tank 12 litres - standard on 2.0 TDI models but can be upgraded at no cost to 24 litres

 

Is this just a little bit cheeky - run a standard car with 40 litre fuel tank for the official EU fuel consumption test to get a low figure, knowing full well that most buyers will opt for the bigger tank FOC?

 

There is no technical data based on differing sized fuel tanks - surely this would impact on the fuel consumption.

American Roadtester / Journalists testing Euro 5 or 6 vehicles with Adblue seem to get & report quite amazing MPG's with or without cheats.

As good as European Economy, 

which is odd given that you get less fuel in a Gallon in the US.

 

As it is it is all kiddology since nobody commutes or travels while on a rolling road in a temperature controlled building.

Then some people drive alone in the car with no Spare Tyre and other might put 5 people and some luggage in 

and fill the tank before setting off.  Driving the vehicle at the 'Revenue Weight'.

All testing should be done with the vehicle at Maximum Weight in the outdoors, and then you have some chance 

of bettering that if you weigh 60 kg and nobody travels with you.