 Scott McClendon with CBS2 News for News Talk KBOI. According to estimates by the U.S. Department of Energy, running your air conditioner on long road trips can lower fuel economy by as much as 25%. AAA is sharing tips to help cool down your car more efficiently. Find a shady spot to park. When you start your car, roll down all the windows and use fresh air mode, the non-circulating, to help flush the warm air from inside the vehicle.