Fuel economy

devizes18193

What is better 30mph with aircon , or with the windows down?

moonrakerz

If you do a search

a. on this site
b. on Google

You will find about 12,876,467 answers to your question I'm afraid !

cepheus

In general windows/fan only is better at low speed, aircon at higher so I would say the former. Reason is because open windows compromise the aerodynamics of the vehicle, but air drag is insignificant at low speeds.

Coveredinbees!!!!

drive at 25 and put the aircon on if it's that big a deal

waynedance

if you have aircon use it, difference is not worth worrying about. Had my car 8 years and tried with and without on many tanks of fuel and no change.

FATBALLZ

I remember watching a program where they tested this, two cars with same amount of fuels one with aircon on one with windows down. Windows down lasted much longer, despite the computers fuel economy readings suggesting there was no difference. Not sure what speed they were going at, but it was a big circular track.

mkirkby

Also saw a test in Autocar many many years ago.

Windows down used about 5% more fuel. Aircon about 10%.

But that was on a small four door car in america with very little power. I would imagine the percentage of extra fuel used with aircon in a larger car would be much less.

Eric_Pisch

its all about speed and air resistance, been done to death on myth busters

at lower speeds 30 and under windows open

at higher speeds where drag becomes and issue with open windows (50+) aircon uses less fuel

DaveMacD

^ +1

Myth Busters tried it and found no difference. They then re-visited it a later date, and found that the speed they tested at (which I think was around the 45mph mark) is exactly where the economies are equal. It will vary slightly depending on vehicle (what with different aerodynamics values and aircon efficiencies), but aircon is more economical and more comfortable at higher speeds, while driving with your windows open is better around towns. But if you're stuck in traffic on a windless, cloud free day in the height of summer, I'd be damn sure that economy would take a back seat

harveybobbles

If you're that worried, then give up driving and use the bus...

mickeypops

Never mind the fuel economy, what about the racket from open windows? Give me a nice quiet ride with the aircon on when needed any day...