The salesman just told you what he thought you wanted to hear, minus the usual disclaimer, "your mileage may vary".
I think the key issue is: your usage patterns don't align with the way the vehicle was tested in order to determine its fuel economy rating. Therefore you don't get the rated economy.
I'd be willing to bet there's nothing wrong with the car, but maybe you'll discover something. Good luck, and keep us posted!
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View my fuel log 2014 Mirage ES 1.2 manual: 62.4 mpg (US) ... 26.5 km/L ... 3.8 L/100 km ... 74.9 mpg (Imp)