Hi Andi and welcome to the forum
You should be getting between 'above 30 MPG to just over 40 MPG at best' in the petrol Ecosport.
16.5 MPG is awful and something is really wrong there.
Its time to put it into a garage to find out why you are getting such losses.
Maybe a cylinder is not firing, maybe a coil pack not working, does the car engine sound rough and staggering at idle.
A service would help, replacement spark plugs, oil and filter, and air filter.
Ensure tyres are at correct pressure.
Auto box can cause losses....
Is it slipping a lot through the gears, does it seem to be coasting all the time, ie, no power behind it. Taking a long time to get up the gears. This would indicate that you have the wrong exhaust back box fitted, that has reduced engine back pressure. Ensure you have the proper back box for the car. Good Luck.