I have five months old Honda City MT 1.3 and my elder brother bought a new Honda Brv MT. We planned a family trip to khewra salt mines and then to Nathia Gali and back, before departing from Lahore we both had our cars fuelled up to max from same petrol station (PSO). We went to the salt mines and the fuel average of my car Honda City gave around 15 km/L with average speed around 130kmph on motor way with four passengers onboard. On the other hand, my brother's Brv gave 12.5 km/L with seven passengers on board. When we refuelled our cars on the way to Nathia gali, the cost of refuelling of Honda City was 3200 rs and 3300 rs for BRV. Furthermore, whenever we refuelled our cars we always refuelled to max and from same gas station, also we drove together.
The point I am trying to prove is that the practical difference between cost of fuel is almost negligible between for example 12.5 and 15 km/L average. I chose Honda City 1.3 MT for utmost fuel average but if I had these stats I would have chosen City automatic or City 1.5L atleast.
I hope this article is insightful and helps in choosing the right car.