We conducted 3 tests with the Toyota Glanza, the rebadged Maruti Baleno: AC on windows up, AC off windows down, and AC off windows up

Fuel efficiency is a top priority for Indian car buyers, especially when cruising on highways at normal speeds. However, some people believe that turning off the AC and rolling down the windows can further improve their car’s mileage. To test this, we conducted our own experiments.

Parameters

We used the Toyota Glanza, the cross-badged version of the popular Maruti Baleno hatchback, for these tests. It is equipped with a 1.2-litre petrol engine (90PS/113Nm) and a 5-speed manual transmission. We fueled the Glanza to the brim before conducting 3 tests, each covering a distance of 81km at an average speed of 100kmph. We refueled the car after each test.

Here are the results:

AC ON & Windows Up

In the first test, with the AC set at 24 degrees Celsius and the fan speed at two, the Toyota Glanza consumed 3.74 litres of petrol while covering 81km on the expressway. This resulted in a calculated fuel efficiency of 21.66kmpl. Next, we repeated the process with the AC turned off.

AC OFF & Windows Down

In the second test, we turned off the AC and rolled down both front windows, assuming that this would increase the car’s mileage. However, with the AC off and windows down, the Toyota Glanza actually achieved lower efficiency compared to the AC-on test.

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Why did turning off the AC reduce the mileage? The answer lies in aerodynamic drag. When driving on the highway at high speeds, the car has to counter the air resistance. Opening the windows allows air to enter the cabin, creating drag and affecting the car’s performance. To maintain speed, the engine has to work harder and consume more fuel. Therefore, driving with the AC off and windows down actually reduces fuel efficiency.

On the other hand, at lower speeds within the city, the impact of aerodynamic drag is minimal, so turning off the AC and keeping the windows down can improve fuel efficiency. However, this is not the case during highway cruising. But what if we turn off the AC and keep the windows up?

AC OFF & Windows Up

In our third test, we turned off the AC, kept the windows up, and set the blower speed to two for occupant comfort. By eliminating the aerodynamic drag caused by open windows, the engine had to work less, resulting in the best fuel efficiency of 23.47kmpl.

Verdict

Based on our results, it is clear that driving with the AC off and windows down does not significantly save fuel during highway drives. In fact, it can even result in higher fuel consumption. Therefore, it is better to keep the AC on and windows up for a comfortable driving experience. However, in the city with lower speeds and less aerodynamic drag, turning off the AC and keeping the windows down can improve fuel efficiency. Keep in mind that this technique is most effective in cooler weather conditions and should not be used in high temperatures, as it may affect driver attentiveness during the journey.

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