Get your fuel consumption display checked on a computer first. Then as a desi method, top up your tank, run your car for 100 km and then again top up your car's fuel tank. The difference of first top up and second top up would give you a picture of how much actual mileage your car is giving to you. I have GLi 2010 who's average fluctuates between 12.5 to 13.5 km/L on an average speed of 26 km. Check yours!