(03 Aug 2014, 11:15 am)G-CPTN wrote My son has a diesel Ford S-Max (people carrier).
He refuses to use the air-con 'because it uses more fuel', yet will travel with the windows open (which causes more drag and uses more fuel . . . ).
I have worked out air con reduces my fuel economy by approx 10/20 mpg whilst using the car.
Obviously if I can stretch out the fuel I have and reduce costs, I will use the air con as sparingly as possible.
I was using that logic when posting the previous message on theories why drivers don't use air con.