Your mileage (fuel average) is determined by the car dividing the distance you've driven since the value was last reset (in kilometers) by the amount of fuel consumed in liters.
This includes time spent while your engine is idling and you're not moving, since the engine is still consuming fuel.
Try putting in a known quantity of fuel, like 10 or 20 liters, into an almost empty tank, or when your fuel reserve light is on, and then drive normally. Reset your fuel consumption average indicator when you fill up as soon as you leave the petrol station.
Then, on the next fuel fill up, check how many kilometers you were able to drive on that fixed fuel quantity before you ran out or the fuel reserve light came on. Divide the kilometers by liters and you'll have your average fuel consumption. The number on your gauge cluster should be very close to this.
If it is, your fuel consumption display is accurate.
If you're expecting your Mira to deliver 30km/l or even 20km/l, it's not going to happen in stop-and-go city traffic.
