Khaberni - Many drivers believe that turning off the car's air conditioner and opening the windows is the best option for saving fuel, however, studies suggest that the answer is not constant across all situations but depends largely on the car's speed and design.
A study conducted by researchers from the Oak Ridge National Laboratory in the US showed that operating the air conditioner at full power consumes more fuel than driving with the windows open at speeds ranging from 64 to 113 kilometers per hour in some vehicles, but the situation changes with an increase in speed. In one of the cars tested by researchers, driving with the windows open at about 129 kilometers per hour consumed more fuel than running the air conditioner, due to a significant increase in air resistance. In another vehicle, operating the air conditioner continued to consume more fuel even at higher speeds.
Researchers explain this by stating that opening the windows disrupts the aerodynamic flow of the car, increasing air resistance and forcing the engine to exert more effort to maintain speed, while the air conditioner adds a relatively constant load to the engine. Therefore, the break-even point between the two options varies depending on the type of vehicle and its aerodynamic shape.
An earlier study published by the American Society of Automotive Engineers (SAE) found that operating the air conditioner had, in the tested vehicles, a greater impact on fuel consumption than opening the windows, but it confirmed that the extent of this effect depends on driving conditions and the type of vehicle.
Experts conclude that driving in cities at low speeds makes opening the windows a more fuel-saving option, as air resistance is limited. However, on highways, closing the windows and operating the air conditioner is often the more efficient choice in many modern cars, since air resistance becomes a major factor in increasing fuel consumption, with results still varying from one car to another.
