To Use or Not to Use A/C in the Car...That is the Question

I read something this morning, which surprised me, but made a lot of sense...Rolling down the windows in your car instead of turning on the A/C seems like a good idea and well-intentioned from an eco-friendly aspect...However, rolling down the windows reduces the fuel efficiency of your car up to 20%...So it was suggested to roll up the windows, turn on the A/C and enjoy...Feel comfortable about feeling comfortable! I like this idea!