How is the fuel consumption calculated?
Basic rules:
- at least two full fill-ups are necessary for the calculation of the first fuel consumption average.
- first full fill-up is used to fix a starting-point.
- real calculation will be started after the first complete fill-up.
- after the second full fill-up, the first fuel consumption average should be appeared together with other fuel consumption related results. 
- later, these results will be calculated and displayed in case of every complete fill-up. 
- all the fill-ups must be recorded. In case of missing records the calculation and reports will not be correct.