ya in a way it does.. i know that it takes a lot of power to pump the ac. running the ac also makes your car run hot bescaue the ac needs cool air just like you radatior but your ac cooler is in front of your radatior for your motor robbing it of cool air.. so all that load on the motor makes the gass milage go down. the same thing aplies to new cars but not as nearly as much as old cars. a help full hint if you car is overheating and your on the road. turn on the heater full blast. that acts like a nother radatior alowing hot water to cool off in another place.. thats why it takes so long in the winter to get a hot heater bescaue your making it extra hard on your car to warm up for a qucker heater turn everything off till it gets warm than turn it on..