The relationship between the car’s AC system and its mileage is quite toxic. You often worry about having the car’s AC ON for a longer period of time and the major concern for that is the mileage. So should you never run your car AC and try to get the best fuel mileage?

But this concern is valid because an air-conditioning (AC) system can increase fuel consumption by up to 20% because of the extra load on the engine. This does not mean that you should never turn your car’s AC. There are a few things that need to be kept in mind.

What happens when the Car’s AC is turned on?

We all know what exactly an AC does, but how and what parts are involved in it is still a mystery to most of us. 

An AC does not create cool air, but it helps in cooling by removing the hot air and moisture. The major components involved in keeping it working involve:

  1. Refrigerant R-134a or Freon is commonly used in modern cars but nowadays the ones with a Global Warming Potential (GWP) less than 150 are being developed. 
  2. The compressor, which runs on 12V is powered by the serpentine belt which compresses the refrigerant into a liquid. This adds to the engine load as the compressor starts running when the car starts. 
  3. The condenser removes the heat from the compressed gas by cooling it down and converting it to liquid. 
  4. The evaporator allows the low-pressure liquid refrigerant mist to flow. A blower motor is provided to push air across the cold tubes of the evaporator to deliver cooled air into the passenger of the car.
  5. The orifice tube restricts the flow of the refrigerant to change from high-pressure to low-pressure liquid mist before it enters the evaporator.
  6. The accumulator is a holding tank for the refrigerant coming out of the evaporator. 
  7. The high capacity exhaust fan will be also be turned ON when the AC is ON.

What are the factors affecting the mileage of the car, due to its AC system?

Car AC

Car AC | Source

The power requirement of an AC system is enormous. 

  • The high clutch and brake usage put a considerable amount of pressure on the engine. Whilst this, if you turn ON your AC, fuel consumption will be high.
  • When you start the car with the AC turned ON, the mileage decreases by 1-2km/L of the total fuel economy of the car.
  • More often you notice a slight load when the AC is turned ON because the pick-up of the car reduces.
  • Notice the Engine RPM meter. When the AC is ON, the engine RPM increases by 200-500, which is a significant rise in the engine load.

Efficient ways to use the AC

  • Make sure that the AC is not turned ON while starting the car to prevent any sort of damage to the engine. When the engine is turned ON, it takes few minutes to warm up. So it is advised to turn the AC ON, only after the car engine has warmed up and is all ready to go. It takes nearly 30 seconds-1 minute to warm up the car.
  • Keep the AC settings in such a manner that the internal air is circulated again and again. Letting the external air inside the car will increase the workload on the AC, to cool down the outside hotter air. It’s better to roll down the windows to let in some fresh air.
  • The AC functions only when the engine is turned on. Otherwise, if the button is pushed in only the fan will be running, which runs on the car battery. 
  • The filters used in the AC vents collect the dust and let out only pure, fresh air. Make sure to keep a check on these filters and replace them periodically.
  • Make sure the Car Refrigerant pressure is sufficient, while the car is still(high) or while it’s running(low). So depending upon the refrigerant and also on the car AC capacity, the pressure varies.

So whenever your car is serviced, make sure to, ask them to check the refrigerant condition and also inform them of the top-up. The low-pressure condition is the biggest reason why the cooling reduces.

Also, read 10 Ways You Can Get Best Mileage Out Of Your Car!

Remember the basic formula: low speed= AC OFF, constant high speed = AC ON

And you are all set to get the best out of your car. Still, there might be other reasons for the drop in fuel mileage. Get your car inspected today by expert Pitstop mechanics. Book your car inspection now.