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Does using an air conditioner affect fuel consumption?

I have always understood that running the air conditioner causes an increase in fuel consumption. Last week, in very cold weather, I was taken for a demonstration drive in a new Toyota Avensis. The dealer kept the air con on all the time. When I queried this practice he said it makes hardly any difference to the MPG figures. Is he right?

Asked on 2 February 2013 by JM, Prestbury

Answered by Honest John
Yes. In summer the a/c uses more fuel than opening the windows up to about 40mph. Over 40mph the extra drag caused by opening the windows uses more fuel than the a/c. In the situation you describe, the a/c probably needed to be on to dry the air in the car and keep the windows clear. If a car has a/c it’s best be run for 10 minutes every week right through the winter, in order to keep the system's seals lubricated and gas-tight.

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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