Mk7 fuel problem

[Jacob2000]

Hi I have a fiesta mk7 1.25 (2010) and recently my fuel hasn’t been efficient, at the moment I have done 92 miles with half a tank, I do about 20 miles a day and there is no leaks from my car, anyone know what could possibly be the problem. Thanks 

[Blatto]

Is there any noticeable loss in performance along with this?

[Jacob2000]

Nothing, I had a custom exhaust back box changed, but if anything after that the car feels faster and haven’t noticed any performance loss

[Meep]

Not wishing to start a fuel debate but which vendor are you using for fuel?

In my 125 Ecoboost I used to use Tesco, power started dipping as you mention, then engine management started coming on. Sought advice and was informed how to reset the light (steady on driveable, flashing do not drive). Switched to Shell V-Power and after several tanks performance was back to normal.

Investigated and was informed the most likely cause was carbon build up that the V-Power additives have cleared.