Most cars these days have a cooling fan that only runs when needed.The advantages in fuel economy ,warmup time ,pollution,HP are well documented elsewhere.The popular methods are the electric fan and the viscous coupled fan.The basic idea is that the fan runs when the engine is hot and does not when the engine is cold .If the car is running at speed the airflow through the radiator grill increases .At a certain road speed the flow may be enough to cool the engine anyway .What would this speed be ? Would it be worth it to shut down the fan at high road speeds?
Since the fan is thermostatically controlled, it will automatically shut off when the natural air flow through the radiator is sufficient to keep the engine cool. The speed at which this occurs will vary based on the car and weather on a given day.
Never heard of anyone disabling the fan. I have heard of people partially blocking the radiator opening in sub-freezing weather to prevent over-cooling the engine.