Majority people in Pakistan rely too much on the information shown in the gauge calculator, that one is never accurate, please use an app on your phone to track your fuel expenses and mileage.
For example, I am using an app called DRIVVO, it can carry multiple profiles meaning if you have multiple cars you can add fuel and other expenses for all cars separately. Also the reports generated by the app are very thorough for me and it gives me the actual fuel consumption of my cars based on the number of liters of fuel I used as I only refuel the car fully, never go for partial refueling.
If you have any questions, feel free to ask.
P.S. according to the app, my GLi is doing about 14-15kmpl on average while my 2.0D has been consistently giving me 16-17kmpl on average in city driving.