Is there an optimum way to use the car AC? Such as low ac/high fan vs high ac/low fan? I usually keep alternating between on and off depending on the temperature of the cabin. I'm guessing the target temperature difference between cabin and ambient will also determine the power.

Any advice would be appreciated. Thanks!

  • What is the ultimate goal? Is it temperature or fuel efficiency or engine power? Commented Aug 12, 2017 at 16:21

1 Answer 1


Sounds like you have a manual AC system on your car. You can emulate how automatic AC systems work:

  • When cooling the car initially, use high fan speed with AC on, and have the airflow mix control set to coldest possible
  • When the car has been cooled adequately, turn fan speed to low
  • If it's too cold now, mix a bit of warm air into the cold air by adjusting the airflow mix control

Note that the last stage (mixing a bit of hot air) probably doesn't improve your fuel efficiency much (it can have a small effect on modern variable cooling rate compressors, but the effect is very small). However, turning fan speed to low may improve your fuel efficiency somewhat because most AC compressors nowadays have a variable cooling rate, and given such a compressor, it's wasteful to blow cold air continuously at a very great rate.

Me? I just start driving the car with temperature set to 21 degrees Celsius, because I have an automatic AC. The car computer does all of these adjustments for me.

  • I wouldn't call mine too modern (2008 Corolla). So, fan speed is not purely electrical (it stresses the compressor too)? Commented Aug 12, 2017 at 23:57

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .