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Is this a wind up?

My sister-in-law purchased a Hyundai i10 under the Scappage Scheme 12 months ago and is highly delighted with the car. During the recent hot spell she has been using the air conditioning but insists on switching it off after just a few miles as she claims that it increases the fuel consumption. However, she then drives with the windows wound down to stay cool. I appreciate that an air con unit will make a small difference to the overall fuel consumption, but surely driving with windows down spoils the aero dynamics of the car and will in itself cancel out any advantage gained by switching off the air con unit in the first place. I would appreciate your views on the situation.

Asked on 14 August 2010 by NM, Salisbury,

Answered by Honest John
In traffic at low speeds, opening the windows is more fuel-efficient than using the aircon. When driving at speed, opening the windows is less efficient than using the aircon because of the turbulence this creates (like driving a sail against the wind). I speak from 54mpg over 7,500 miles in a FIAT 500 1.2 petrol fitted with a/c. See eco driving video lesson at: www.honestjohn.co.uk/news/green-motoring/2010-06/r...1 , where this specific question is asked and answered.

Real MPG enables you to register the fuel economy you are actually getting against your make and model of car, its engine and type of transmission.

Every time you enter an average consumption figure against your car, the overall average automatically adjusts to reflect it.

Real MPG
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