Does Driving with AC On or Windows Down Consume More Fuel?
2 Answers
Driving with the AC on consumes more fuel at low speeds, while driving with windows down consumes more fuel at high speeds. Here are the analysis and additional information: 1. Analysis: When driving on highways, the faster the speed, the greater the air resistance. The car's fuel consumption is mainly used to overcome air resistance. Only when all windows are closed does the car have the lowest air resistance coefficient. Opening windows disrupts the car's aerodynamic integrity, increasing the air resistance coefficient and reducing fuel efficiency. 2. Fuel-saving Tips: Maintain good driving habits. When accelerating, the engine must increase power, and every time you brake, the energy generated by this power is lost as heat. Reduce unnecessary weight on the car. The heavier the car, the more fuel it consumes. Control the warm-up time.
I saw some interesting real-world test data online. Driving with windows down at low speeds in the city does save fuel compared to using AC, since the compressor isn't running and engine load is lighter. But on highways, it's the opposite - open windows dramatically increase aerodynamic drag. Data shows that above 80 km/h, open windows can increase fuel consumption by 20% more than using AC, as the car has to push aside extra air. I tested this with my 1.6L car - on summer highways, using AC burned about 0.5L more fuel, while driving with windows open surprisingly consumed 0.7L extra! Though to be precise, vehicle condition matters too - if an older car's compressor is worn out, running AC becomes more taxing.
