Not sure why so much hate, I bought this for my wife, I personally have a 2014 City (1.5, Prosmatec) and the fuel economy difference is day and night. Pixis (Toyota's Mira alternate) is giving 19.4 km/l theoretical (as shown on the speedometer) and 18.7 km/l (actual, calculated over 700+ Kms in Islamabad drive).
If you are getting 10 Km/l then you are either driving too hard or you have an engine that's a lemon.