Torque Shop: Is driving with windows down a good practice?

Driving a convertible with the top down and with the air-con on will have a noticeable negative impact on a vehicle's fuel efficiency. PHOTO: ST FILE

When I drive in the early morning or late at night, I will switch off the car’s air-conditioner and wind down the two front windows about a third. I observe that the petrol consumption is lower when I drive in this manner. Is this a good practice? How will it affect my car?

Driving with the windows down can increase drag and adversely affect the vehicle’s aerodynamics. This, in turn, will have a negative impact on fuel efficiency.

The precise impact will be influenced by how much drag there is, and this will be a function of factors like speed, and how many windows are open and whether they are fully open.

Meanwhile, running the air-con also consumes energy. How much energy is consumed depends on things like the prevailing ambient temperature, the selected temperature setting, and whether the car has a multi-zone system which can deactivate one or more zones.

If you are indeed experiencing better fuel efficiency, it must be because the amount of fuel saved from not running the air-con is more than the additional energy required to overcome the increased drag.

There are no detrimental effects associated with driving with the windows down, except for increased noise level and, perhaps, more dust and fumes entering the cabin.

Join ST's Telegram channel and get the latest breaking news delivered to you.