The fuel economy stated by the factory is measured in perfect laboratory conditions on a rolling road without brake pads, fan belts and everything else that gives resistance.
Spare tyres are removed and there is only 1 litre of fuel in the car during these tests. The tyres are inflated to way over the normal pressure and only a 5 kilo driver is sitting in the car. I just cant understand how your cars give the same mileage claimed by the factory done in the above conditions.
These perfect conditions does not exist in the real world on the roads.