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Each motorist seeks to reduce its fuel consumption, especially with prices that rise steadily. It is often thought of the tyre pressure, engine maintenance or driving style. But few people know that such a benign gesture as opening windows can have a significant impact on fuel consumption. A question then arises: do you have to roll windows open or closed to save fuel? The answer is more surprising than it seems.
The unsuspected impact of air on your consumption
Air is an invisible but formidable adversary for your vehicle. The faster you drive, the more the air exerts a resistance, forcing the engine to provide additional effort. This phenomenon, called aerodynamic drag, plays a key role in fuel consumption. However, the opening of the windows increases this resistance, requiring more power to maintain the speed.
On motorways, from 80 km/h, open windows create a real aerodynamic brake, making your car less efficient and more fuel-intensive. Conversely, at low speed, especially in the city, this phenomenon is much less marked, which makes it possible to use windows without major impact on consumption.
When to open or close windows to save fuel?
High speed windows closed for better aerodynamics
When you drive at high speed, especially on the highway, open windows increase the drag of the air, forcing the engine to consume more energy. It is therefore preferable to keep the windows closed and to opt for ventilation or air conditioning (in economic mode if possible). Contrary to popular belief, well-adjusted air conditioning often has less consumption compared to high-speed wide open windows.
Tip: If you need to use air conditioning, give preference to a moderate temperature (around 22oC) to avoid unnecessary overconsumption.
Low speed: focus on open windows
In the city or on low-speed journeys (less than 50 km/h), the impact of the air is negligible. In this case, it is more economical to open windows to ventilate the passenger compartment rather than to switch on the air conditioning, which can increase fuel consumption from 0.3 to 0.5 litres of fuel per 100 km.
Tip: When you are stationary or in traffic jams, also give preference to opening the windows to prevent air conditioning from consuming fuel unnecessarily.
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