A method and control arrangement for controlling operation of a fan in a cooling system of a vehicle, wherein operation of the fan is controlled based on a temperature of a coolant in the coolant system meeting a set-temperature of the coolant. The method comprises monitoring an engine oil temperature of an engine of the vehicle during a plurality of driving cycles with the vehicle; and adjusting the set-temperature of the coolant based on a measure indicative of a plurality of maximum temperatures of the engine oil during the plurality of driving cycles.