We don't have enough information to give you any advise yet,
We don't even know if it's a engine problem, or rolling resistance problem
Or none existence, different driving, new road works, different traffic conditions and so on
How long have you had the the car
Which engine
Long term, fuel trims, reading
What is the temperature gauge reading, how long does it take to get to temperature
What is the outside temperature
What are the tyre pressures
Do any of the the wheels feel are smell hotter than the others
Does the exhaust smell of fuel
Is there any smoke out of the exhaust
Does the exhaust, sound smooth is there's slight ticking noise
Is there any loss in performance
Colour of the plugs
O2 sensor pre and post catalytic voltages
Inlet manifold pressure
Fuel leak
Roof box, Aircon and many