Windows down or air con on?

My 60 Nissan Micra has air conditioning.
I am told that using this dramatically increases the fuel consumption.
I am also told that having the windows wide open does the same.
What is the truth ?

Asked on 25 July 2012 by Georgegm

Answered by Honest John
At low speeds, in traffic, a/c on increases fuel consumption, so better to run with the a/c off and the windows open.

At higher speeds (above 40mph), windows open create more drag and increase fuel consumption to a greater extend than a/c on, so best to run a/c on and windows closed.
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