To me using fresh vs. recirc is a safety issue . Let me eloborate . When you use recirc it also recircs the moisture that you exhale . That moisture accumulates on the glass . You can really notice this effect at night or when it rains . Believe it or not when it rains , if you use recirc , there will be more moisture in the car than outside . Besides if someone farts (poot if you are a girl) , you will get to enjoy that for a while also
Lets review . If it is raining and your window are fogged , use fresh air , a/c and the defrost vent and your fog will magically disappear . B/C it is evaporating the moisture on the glass .
I don't know why vehicles have a recirc . Think about this , with recirc , every breath you take , there is LESS oxygen , which would make you drowsy .
I don't know about you peeps , but I deserve fresh air ALL the time