With the hot days coming, many drivers put the same question again: Can I save more fuel to keep the windows open or when turning on the air conditioner? The answer is not that obvious, because it depends mainly on the speed to which it drives. And, according to a recent study, this difference can have a direct impact on the wallet.
The Spanish newspaper El Economista, quoted by Executive Digest, released a study by the Society of Motor Engineers (SAE), which sought to clarify this doubt. Through practical tests, it has been proven that the speed of the vehicle plays a determining role in the most economical choice between air conditioning or open windows.
The turning point identified was 64.4 km/h. Below this speed, circular with open glass is more efficient. Above it, the air conditioner becomes the best option to save fuel.
The tests in wind tunnel
To reach this conclusion, the investigators resorted to a wind tunnel of General Motors. Two models with powerful engines were used: a 4.6 liter V8 sedan and an 8.1 liter V8 SUV. Each vehicle was tested at speeds of 50 km/h, 80 km/he 110 km/h.
The goal of the engineers was simple: to realize how consumption varied with the use of air conditioning and with open glass, under different driving conditions.
Low consumptions, high penalty
At reduced speeds, such as 50 km/h, tests showed that air conditioner maintains a stable consumption, but it represents an increase in total consumption between 5% and 10%. Since the entry of windows through the windows does not significantly affect aerodynamics, the most economical choice is really to walk with open glass.
This conclusion applies mainly to urban pathways, where frequent starts and braking maintains the average speed low. In these contexts, turning off the air conditioner can translate into a real savings at the end of the month.
Above 80 km/h, the scenario changes
However, when speed exceeds 80 km/h, the impact of open glass becomes visible, the same source refers. Increasing air resistance requires the engine to work harder to maintain the pace, and this translates into higher consumption.
The data showed that sedan lost 20% of efficiency at 112.7 km/h with open glass. In the SUV, the loss was 8%. Despite the difference between models, the recommendation was clear: on the road or highway, it is better to close the glass and turn on the air conditioner.
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Each car reacts differently
It should be noted that this study was done with large vehicles. In other models, with different aerodynamics, the numbers may vary, but the logic remains. Aerodynamics influences consumption, and the higher the turbulence caused by open glass, the greater the engine effort.
In smaller or city cars, the impact may even be higher at medium speeds, because they are lighter and less prepared to deal with the drag of the air, the engineers conclude by the same source.
What to do on urban routes
Within locations, with constant traffic, traffic lights and reduced speeds, the best option seems to continue to keep glass open. It allows to refresh the interior of the car with less impact on consumption and avoids the continuous effort of the climate control system.
Even on warmer days, it is enough for a few minutes with the glass open to help balance the temperature, especially if the vehicle is in shadow or slow motion.
Small habits that make a difference
If you choose to use the air conditioner, there are ways to do so more efficiently, the engineers also refer to. Open the glasses for the first few minutes to expel the accumulated hot air helps. Regulate the temperature moderately, instead of using the maximum, also contributes to saving fuel.
In addition, regular maintenance of the air conditioning system, including the verification of soda gas, avoids unnecessary consumption and ensures better performance.
Saving fuel also goes through simple decisions
SAE’s study shows that there is no unique response to all cases, but a useful practical rule: below 64 km/h, download the glasses. Above this speed, close everything and turn on the air conditioner. This choice, applied aware of your type of driving, can result in considerable savings over time without compromising comfort behind the wheel.
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