How fuel efficient is the Altroz iTurbo, as claimed by Tata?

The Altroz iTurbo has an ARAI certified fuel efficiency of 18.13 km/l, according to Tata. But sometimes official mileage figures are very different from real world and petrol turbo engines are very sensitive to style of driving. On the highway runs, some owners get close to the claimed figures, while others only manage 12–13 km/l in city conditions. Although the iTurbo has a higher ARAI rating, there's doubt if it is actually more efficient than the NA version in real world use. Climate, traffic conditions and individual driving habits are all factors. Others, too, argue that the higher purchase price of the iTurbo negates its potential fuel savings. Given fuel prices are always in flux, people are interested in the true long term economy of the iTurbo compared to other options in its segment, whether they are a potential buyer or already have one.