As I have always done all my cars, I control the consumption from the first day.
Because you always fill the tank is fairly reliable method of the "rule of 3", and to verify the difference between consumption "real" and marked by the car's computer "FIS".
According to official data, the TT 1.8T 163 hp of consumption has the following:
Urban consumption: 11.1 l/100 km
consumption intercity: 6.3 l/100 km
average consumption: 8.1 l/100 km
In this section I will update the graph showing consumption "real" and "FIS" after each deposit.
Dashed line indicates the consumption RED "Real" (calculated by rule 3, taking into account the kilometers traveled and the liters in the tank entered).
Dashed line indicates the consumption GREEN "FIS" (indicating the onboard computer, going to put gas, setting it to 0 after filling the tank).
In the squares of the Y axis is indicated the real average consumption and average consumption of FIS before and after adjustment (see section "VAG-COM" in the left menu on setting the consumption indicated in the FIS). .
Here is the graph (click to enlarge):