If the car suddenly starts using more fuel, the change is worth noticing even if there are no other symptoms. Sometimes the reason is simple, such as shorter trips, colder weather or a heavier right foot.
In other cases, higher consumption can point to a technical issue. Incorrect tyre pressures, a dirty air filter, lightly dragging brakes or a sensor fault can all affect how efficiently the car moves.
It is useful to compare consumption over a longer period rather than based on a single day. If your service history includes dates, mileage and notes, it becomes much easier to see when the change actually began.
If the increase stays constant and there is no obvious explanation, the car deserves a check. Fuel consumption is often one of the first signs that something is no longer working as well as before.