The trick for cooling your car that science has declared to be the most effective

27.06.2026. 4:55 p.m

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Science and a few simple tests have revealed a surprisingly effective method that saves both time and fuel.

There is almost no worse summer feeling than opening the door of a car that has been sitting in the sun for hours. A rush of hot, stagnant air, hot metal parts of the belt and a steering wheel that is too hot to touch are the well-known pain of every driver, reports Net.hr.

In such moments, the first reaction is to turn on the air conditioning and wait. But what if that’s not the fastest way to turn your mobile stove into a cozy vehicle? Science and a few simple tests have revealed a surprisingly effective method that saves both time and fuel.

A greenhouse effect on four wheels

Before moving on to the solutions, it is important to understand why the car gets so hot. The answer lies in the greenhouse effect. The sun’s rays pass through the glass, and the heat remains trapped inside. Surfaces like the dashboard and seats absorb that heat and then radiate it back into the cabin, raising the temperature well above the outside.

Stanford University research showed that during a sunny day, with outside temperatures between 22 and 35 degrees Celsius, the temperature inside the car can be as much as eight degrees higher on average.

In just ten minutes, the cabin can reach more than 50 degrees, turning into a dangerous zone. The dark dashboard acts like a radiator and radiates heat long after you turn on the cooling.

How to cool the car quickly?

In order to find the fastest way of cooling, a multi-day experiment was conducted: in a car parked in the sun, it was measured how quickly different techniques lower the temperature. The results were dramatic.

The first method – starting the car and turning on the air conditioning at maximum while the vehicle is stationary – proved to be the least effective. In the first ten minutes, the temperature dropped at a rate of only one degree per minute. After 20 minutes in the car, which was 53 degrees at the beginning, the temperature only dropped to 39, which was still higher than the outside temperature. Driving is key because the air conditioner needs airflow over the condenser to work efficiently.

Another methodapplied by most drivers, involved driving with the windows open for the first two minutes with the air conditioning on. It proved significantly better, lowering the temperature by 2.5 degrees per minute.

The surprise arrived with the third method – driving with the air conditioning on, but the windows closed. Although it seems illogical, this technique proved to be even faster, lowering the temperature by 3.1 degrees per minute. The explanation is simple: by opening the window, you release the hot air, but at the same time you also release the precious cold air that the air conditioner is just starting to produce.

The winning method and the science behind it

The absolute winner of the test, with a temperature drop of 3.6 degrees per minute, was a method that may seem unusual at first glance, and is sometimes called the “Japanese method”.

The procedure is simple: before entering the car, roll down the window on the passenger side. Then forcefully open and close the driver’s door five to six times, using it like a fan.

This move is not magic, but applied fluid dynamics. As mathematician Hannah Fry explains, swinging the door quickly creates a low-pressure area inside the car.

That “vacuum” literally sucks in the hot air and pushes it out through the open window, while cooler air from outside enters to fill the space. The test showed that after this procedure and subsequent driving with air conditioning, the temperature in the car dropped to a pleasant 30 degrees after 20 minutes.

Of course, this method has its limitations. Some experts warn that if the outside air is also extremely hot, you’ll just be replacing one hot air with another. Also, swinging the door too hard can damage its hinges over time.

The best way to fight heat is prevention. Parking in the shade or using a windshield protector always helps. However, once you’re in front of a red-hot cabin, the science is clear.

The fastest strategy is a combination: use physics first. Lower the passenger’s window, “air” the car a few times by waving the driver’s door, then sit down, turn on the air conditioning to maximum and immediately start driving with the windows closed. It is the fastest way to a pleasant drive, reports N1.