During the hot summer, a car left under the scorching sun can turn into a sweltering oven, with interior temperatures easily soaring above 60°C. At the same time, interior materials like the dashboard and seats can release volatile gases in the heat. Addressing this common issue, renowned Spanish mechanic Juan José and Spain’s General Directorate of Traffic (DGT) have offered expert advice, pointing out a common mistake most drivers make in their first step to cool down the car.
The Common Mistake: Closing Windows and Blasting the AC
Many drivers have a habit of getting into their car, immediately closing all the windows, and turning the air conditioning to its maximum setting. Mechanic Juan José points out that this method is extremely inefficient. The AC system has to work much harder to cool the trapped, scorching air inside the cabin, which not only cools the car down slowly but also significantly increases fuel consumption and engine load.
The Expert Tip: Ventilate First, Then Cool
The correct procedure is to lower the windows completely for a few seconds while starting the air conditioner. Use the airflow from driving or natural cross-ventilation to quickly expel the hot air and any fumes from the interior plastics. Once the initial wave of hot air has dissipated, you can then close the windows and let the AC system work in a relatively cooler environment. This will dramatically improve cooling efficiency and feel much more comfortable.
The DGT’s Physics-Based Cooling Method
Spain’s General Directorate of Traffic (DGT) also offers a quick cooling trick that doesn’t even require starting the engine. Here’s how to do it:
- First, lower the window on the rear passenger side (diagonal to the driver).
- Then, open and close the driver’s side door several times.
This simple action uses air pressure differences to rapidly force the hot air out of the car. In just a few seconds, the interior temperature can drop by nearly 10°C.
High-Speed Driving: Windows Up, AC On is More Economical
Regarding the fuel consumption debate between opening windows and using the AC, the DGT also provides clear guidance. When driving on city roads at speeds below 80 km/h, opening the windows for ventilation has a negligible impact on fuel consumption and is the more economical choice. However, once your speed exceeds 110 km/h, open windows severely disrupt the car’s aerodynamics, increasing drag and causing a sharp rise in fuel use. In this scenario, rolling up the windows and turning on the AC is the more fuel-efficient option, estimated to save about 0.3 liters of fuel per 100 kilometers.
