does running your car with the air conditioner on use up more gas, but?

Question

would not driving with the window down create a drag and cause the car not to get as good gas mileage as if I had the cold air on.

Answer 1

According to this recent article, both of those popular theories are actually myths. Check it out:

http://biz.yahoo.com/cnnm/070515/050907_gas_myths.html?.v=1&.pf=family-home

Answer 2

There have been studies performed on this. As I recall, at highway speeds travelling a continuous distance drag is more of a factor than the extra load of the compressor on the engine.

In stop-and-go, around town driving, you generally don't get up to speeds that really make the drag more of a factor than the compressor. Actually in some cases the extra heat with less air flow can result in the compressor working harder.

That said, I also recall that the increase in gas mileage was not huge, perhaps up to 5% (i.e. instead of 20 mpg, you get 21). What you have to decide is if it's worth hearing your spouse and kids complain about the heat! Even with high gas prices, it might only be a quarter for a trip to the store.

Answer 3

Mythbusters ran a car on a test track to check just the conditions you list.
The condition that produced the worst gas mileage was with the windows down, and the air conditioner off.
If I remember correctly, running with the windows up and the air conditioner on or off didn't make a lot of difference in the mileage, but I find that hard to believe.

Answer 4

Runnig the car with airconditioner on , will consume more gas. The fuel consumption for drag while window is down, at speed within the high way speed limits will be much less than the that due to airconditioner.

Answer 5

It takes extra energy to do either- drive with open windows or to drive with the AC on. Remember, though, that there are varying degrees of energy consumption based on the level at which you operate the AC. You can do what I do- on longer trips, I'll run the AC full-bore for a minute or two to cool the car and then tweak the temperature knob until the air is comfortable, at which point I'll turn the fan up high. It takes less energy to run the blower motor than to run the AC at a colder temperature.

The key to remember with AC is that it is being run by the electrical system, not directly by the engine. The engine is the only element in your car that is being powered by gasoline. All the electrical devices are being run from the battery. It is true that the battery is charged by the alternator which is, in turn, run by the engine. The engine, though,will not run harder or lighter depending on the level of charge of the battery. Because you do need to recharge the battery more heavily, you will decrease the lifetime of your battery by using AC (albeit by a neglible amount).

Answer 6

ac is better, but that's at high speeds like when you're on the freeway, because, you're right, the air drag. but when you're going 30-40 on the streets, windows would be better.