bloody hell...to summarise and to make things simpler:-
Generally it all depends on:-
1) Overall weight of the car, e.g., continental cars are
heavier.
2) Yes it is true, the capacity of the car, e.g., the larger the
capacity, the higher the FC.
The other factors are rather unique:-
1) Technology employed, e.g., Engine Technololgy:- VVTi / iDSI;
Transmission Technology:- CCVT / CVTC / CVT, etc.
2) Electricity driven? Petrol driven? Or both?
3) Ergonomical Design of the car, e.g, is it as aerodynamic as
Honda or Celica?
even if you do not have the best ergonically designed car but has
VVTi or iDSI, your car will still achieve good F.C. efficiency.