This investigation was carried out by me.

Exhaust leak top the charts for high fuel consumption fellowed closely by misfiring. Every other problem are minimum compared to this two.

Many cars in Nigeria has leaks in there exhaust but unknown to the owner. Either a crack in the exhaust or a tiny hole, no matter the size of the leak it can impact the fuel consumption greatly.

To determine if there is leak you have to listen to the sound from a cold start. Preferably early in the morning. If the car make usual sound during a cold start but normalize after the exhaust has warm up. Then you have a exhaust leak.