for my mazda5 2.0 skyactiv, driving from selayang to my office at jln sultan ismail KL with bad traffic jam every morning via jln kuching, fc meter shows 10.1 L/100km. beside fc meter, i also calculate the fc from how much i pump petrol. for example last week, i pump RM 60 petrol, i got 280km before it empty again. so based on the calculation:

RM 60.00/RM 2.10 petrol price per liter last week = 28.57 liter
X = 100km/280km x 28.57
X = 10.2 L/100km

so, more or less same as fc meter. for highway driving normally i get 7.5 L/100km. fc claim by Mazda for the Mazda 3 5.7L/100 km is reasonable i think if for highway driving and light footed.