Nowadays, every car is equipped with air conditioners and offers a comfortable driving experience during the scorching heat of summers. However, there is a constant debate about car mileage with and without AC. It is essential to understand the working mechanism of a car's air conditioner first and whether it affects the car's mileage. 

Let's find out!

The working mechanism of a car's air conditioner is based on the fundamental principle of heat exchange.

Listed below are the following parts of a car's air conditioner that operate in tandem to provide a comfortable ambience inside a car's cabin:

• Compressor
• Condenser
• Receiver Dryer
• Evaporator
• Expansion Valve

Now take a look at how all these components work to provide a pleasant driving experience during summers:

• The compressor compresses a refrigerant and converts this gas into a liquid state.

• This liquid refrigerant flows through tubes present in a condenser, and it comes in contact with air. The temperature of liquid refrigerant and air increases due to high-temperature liquid present in a condenser. In this process, the refrigerant releases heat and mixes with the air.

• Once this refrigerant flows to a receiver dryer, desiccant eliminates the moisture content from this refrigerant liquid and air and generates a cool refrigerant.

• The cooled liquid refrigerant passes into an expansion valve. This lowers the pressure of the fluid and transfers it to the evaporator.

• The evaporator draws the air from outside, and cooled refrigerant liquid converts the hot into a cold one.

• Fans placed close to passenger seats blow the cool air through vents. In this process, the moisture content of the air is also removed, helping you to enjoy dry and fresh air in the car cabin.

• When the cold refrigerant becomes hot, it turns into a gas again. This low-pressure hot gaseous refrigerant circulates back to the compressor, and a new cycle begins to help you enjoy a constant flow of cool and fresh air.

A car's air conditioner affects its mileage to some extent. This is because the air conditioner draws power from the engine to function. This puts pressure on it and forces it to utilise more fuel. If you switch your car's air conditioner constantly to its maximum setting, it lowers the average mileage returns by 30%.

For instance, you can drive approximately 500 km with your car's tank filled with fuel, and the air conditioner switched on. Similarly, you may cover a distance of up to 600 to 625 km without switching on the air conditioner.

The more aerodynamic the car is, there will be greater chances of lower fuel efficiency in the long run when windows are kept open while driving a car at high speed for a prolonged period.

To understand it clearly, you need to learn what aerodynamics is.

Aerodynamics is a study of air motion, especially when it is affected by a solid object. For example, when you drive your car at higher speeds, it experiences an opposing force known as air drag. This puts pressure on the engine to generate more power to oppose it.

Now, your car with closed windows has a much lower proportion of air in it. If you open its windows, the air from outside enters your car's cabin as it travels from high to a low-pressure area. As a result, the car puts pressure on the rear mirror, which is in the opposite direction you are driving.

Consequently, your car will experience more drag if the speed increases and will hamper the car's fuel economy in the long run.

"Are you wondering if you can increase fuel efficiency by driving your car with closed windows and switching the air conditioner on during summer?"

The answer is that your car's air conditioner draws power from the engine to operate, forcing it to use more fuel, impacting your car's fuel efficiency. So, whether your car's windows are open or closed, switching on the air conditioner will lower fuel efficiency to some extent, as explained earlier.

It is ideal to switch off your car's air conditioner when driving in the city at lower speeds to save fuel. This means there will be lesser drag resistance and will not hamper the fuel efficiency of a car. Moreover, the power output of an engine is less at lower speeds. This imposes more pressure on the engine to generate a substantial power for AC to operate.

So instead, turn on your car's air conditioner on highways when driving the vehicle at higher speeds. This way, the engine will generate substantial power to operate the air conditioner. Since the drag will also be higher, keep your car's windows closed to save fuel costs in the long run.

As you can now make out that air conditioner does affect car mileage to some extent. However, it will be comparatively lower at lower speeds than driving a vehicle at high speeds with open windows. Moreover, the effect will be more pronounced with cars featuring aerodynamic designs than in cars shaped like boxes where air movement is not affected.