Why is the radiator fan getting switched on before the thermostat coil in viscous coupling opens contributing in fuel consumption?
The raditator fan temperature sensor has a lower set point than what the thermostat is opening at, if this is something new then suspect thermostat is opening late.
Follow the upper radiator hose from the radiator towards the engine. The upper radiator hose is connected to the thermostat housing on the engine side. The thermostat is under/inside the thermostat housing. Remove the upper radiator hose from the housing then remove the two bolts holding down the thermostat housing then remove the thermostat housing to expose the thermostat.