You can hardly do without air conditioning (air con) in summer. What if we used it in a “responsible” mode?
The first thing to do is to use air con as a last resort because it consumes about 1 liter of fuel every 100 km. However, lowering the windows on the highway would prove counterproductive because the car loses its aerodynamics. In summer, do not start your ride with the air conditioning on. Differences in temperature may damage the system and your windshield if it is weakened. When starting, lower the windows and roll a few with windows open to ventilate. In town, pollution will quickly force you to close the windows. In this case, position your air conditioning system 5 degrees below the outdoor temperature, no more.
As soon as you get out of a built-up area and you can switch the maximum speed ratio, it’s as you want: either moderate climates or wide open windows.