Drive car don't worry about FC.
Worry FC don't drive car.
Really...FC is just a scam thing.
Firstly, FC claimed by manufacturers are skewed.
Second, FC can never be calculated correctly as a driver because you don't drive same road in the same manners every day. You can only average your FC base on numerous fluctuating factors :
1. temperature of the day
2. tyre inflation on that day
3. number of stops at traffic lights
4. waiting time at traffic lights
5. your pedal / acceleration ,
6. weight of car with more petrol or less petrol
7. extra passengers or no passengers
9. Traffic condition on that day
10. air con, mechanical losses
11. rainy or hot warm day
12. your mood, which affects your driving
I think I can list 20 factors than will contribute to FC.
SO.. please dont use FC to gauge your car.
Just drive.
If its poor, blame it on the above 12 items.