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Whats more fuel efficient, driving with the air con on, or driving with windows down?

Public Comments

1. Windows open. If you turn on the air con while driving, you can feel the car lurch. Open the windows and you feel nothing but fresh air.
2. It depends on speed and car model, but there's a program called Mythbusters in Discovery channel where they did a test and it was more fuel efficient driving with A/C on.
3. depends how far the windows are down and how fast you are going. If they are all the way down and you are doing a steady 70 then I would probably opt for the air con as the drag created will really effect the fuel consumtpion.
4. ts obvious with window down..air con gives load on eingine and reduces mielage
5. windows open !
6. driving with windows down
7. Air con eats up petrol like there's no tomorrow. Windows down of course.
8. WINDOWS! It only takes a small amount of energy, used for a small amount of time, to open the windows, wheras using the AC uses a considerable amount of energy nonstop.
9. With the A/C on. The only time I drive with my windows down is if the speed limit is 40 or under. If you are on the highway and ride with your windows down you will burn more gas than with the A/C on.
10. a/c is more fuel effecient as with the windows down it stops the car travelling effeciently
11. Accually, "Mythbusters" determined to leave the windows down in the city and up on the highway. It is also more efficient to leave the tailgate of a pick-up truck closed rather than open.
12. more fuel with air-condition on and more likely to contract rheumatism to the neck and shoulder, while driving windows down.
13. widows down.
14. Cars are designed to be driven with their windows up (wind tunnel tests and drag). The faster you go with the windows open the more it effects the aerodynamics creating drag costing more fuel. So driving around at slow speeds windows open at fast speeds A/C on.
15. Car fuel efficiency depends upon the working of the carbeurator. Added to this, when we drive with windows down, the conserve fuel usage than when we drive with airconditioners on.
16. I would assume driving with windows down but I have kick butt air in my truck so I don't do that
17. They probably equate to the same waste of fuel, however if pressed I would say its better for fuel efficiency to roll the windows down than use the air conditioning.
18. It all depends on the speed and the aerodynamics of the vehicle. As you might be aware the air-con works off the crank wheel on the vehicle so the extra component does use more fuel especially in low speed driving. However, as stated in previous answers its actually more efficient to drive with air-con on at high speeds than it is to drive with the windows down. The drag co-efficient of the car rapidly diminishes when the windows are down so I would suggest at low speeds lower the windows and at high speed use the air con. There is a bit of a conundrum however, think about when you tend to use the air-con?.... Is it usually when your stuck in a hot sticky traffic jam, where an open window is almost useless! Its the worst time to use it but probably the most useful?? So there you go!?
19. DUH...Down, windows....Down!
20. windows down but if its over 85 air conditioner not that its cheaper but a lot more comfortable
21. Below 40mph Windows down - Over 40mph Windows up and Aircon on. All those who say "Doh - Windows Down" are wasting petrol like there's no tomorrow. The drag created by lowered windows is enough to slow the car down considerably. How do you overcome this? You put the foot down and burn more petrol! Even lowering the window an inch is enough to destroy the aerodynamics of the car, so keep them up and switch on your AC. Alternatively - drive with the windows up and air-con off for even more fuel savings!
22. I don't really know but I do now that a dirty air filter and a carborator that isn't working properly could make your car use more gas.
23. if you drive an old p.o.s. car then windows down. however if you have a modern car which was actually wind tunnel tested then its ac on. modern i.e. last 5-6 years or so cars ac pumps are far more efficient than their predecessors. the areo drag you would get by having your windows down is far worse than having your ac on.
24. Of course you've gotten more answers than you know what to do with...but here's one more point to think about...When you use the A/C, the compressor is not on constantly, rather, it cycles on and off as needed. SOOOOO...in addition to the fact that A/C generally uses less fuel on the freeway/cruising over 40mph, also rest assured that you are only using more gas when the the compressor kicks ON. When it turns off, you continue getting the best fuel economy possible (provided your tires are properly inflated and you drive a steady speed) And one more thing...before turning on the A/C, just turn on the blower and see if that blows cool enough air to keep you comfortable.
25. on new cars ie 2 years old the ac pumps are desinged to be eco freindly & only knock down the consumtion by a mile or two, but older cars it is quiet alot so depends on the age of the car.