Hello good people of nairaland and car experts in the house; i need your advice on how to resolve the recent increase in fuel consumption of my peugeot 407.

I recently changed the plugs as adviced by my mechanic. What surprises me most is that the car made a trip 2months back from sokoto state to niger state on a filled tank and had a little below half tank on arrival.

Kindly advice me on a possible and permanent solution to this sudden change... Thank you in advance!