During the summertime, it could be said that the hottest moment between is when you first get into your vehicle. This is the moment that really sets the mood for the trip. I don't know about you, but I don't like to drive grumpy. It opens the door for road rage, of which we already have plenty on our highways.
Cooling down your vehicle quickly before you set off on your journey will reduce your agitation level, heighten your awareness, and enable your vehicle's air conditioning to work less, thus saving gas and CO2 emissions. While this quick cool down method is not exactly nuclear physics, it is a bit of a lesson in applied sciences.
What is Heat? Plus How to Beat it
Heat is basically an abundance of energy. This energy causes the atoms and molecules inside your vehicle to move around at a faster pace, thus taking up more space and increasing the air's density. As we all learned from science class, denser air rises, which puts the hottest air inside any vehicle right where your head is, which is a very unpleasant circumstance!
When you get inside any hot vehicle you must resist the temptation to cool your upper body first as most people tend to do. The first thing you should do is push the hot air out, starting with the hottest air. The easiest way to do this is to set the air-conditioner on fresh-air (not recirculation), crack the windows, set the fan to high, and adjust the air to blow through the lower foot-well openings.
Pushing the air from the bottom vents helps rid the hot air more efficiently than using the upper vents. this is truly the best way to purge the stale air from the entire vehicle in the shortest amount of time. Once the majority of hot air is removed, you can close the windows and adjust the air to blow towards your upper body (if you prefer).
Fresh Air vs. Recirculation
The reason you should never set your air to recirculation in the summertime when you first turn on your air conditioner, is because it draws the majority of air from the interior, which is of course where the hottest air is. Once the air inside the vehicle cools, you can adjust the fan back to recirculate.
The recirculation setting always works best when a vehicle is already at its desired temperature. This allows the air-conditioner to work less (use less energy) to maintain that temperature. If you live in the congested city, the recirculation setting is also suggested, as the CO2 emissions from other vehicles can find their way inside your vehicle when pulling the majority of air from the outside.
To reduce your fuel consumption and CO2 emissions even more, don't forget to turn your air-conditioner off a few minutes before you reach your destination.