air con

[K99]

Does having your air con on in the car use up your petrol?

[marje]

Yes it does apparently.  I wanted an air conditioned car but was told that it uses too much fuel.  I can always open a window!!

[dilligaf]

air con will add about 10% to your fuel bill. Considering the cost per litre its best to keep your window open on the move. Only use air con in queues then only on recirculating in the car.

[Mrs_Pegasus]

Yes it does and so does everything else that you turn on in the car!

Recently i watched Top gear and Jems drove I think a VW on one tank of diesel to see how far it went.  He listed a number of things that would help with the fuel economy and it included the heating and air con. and of course the window being down causes drag on the car and therefore uses fuel. 

Personally I have air con on our cars and use it when i want to for my comfort while driving and do not really watch the fuel gauge because as long as I am comfortable I am alert and can enjoy the drive.

[martyroberts]

Mythbusters did a test and they said that it didn't make a difference.

HOWEVER: I know from experience that it does!

[Loosehead]

Yes it does. The air con is essentially a refridgeration unit being driven by the engine, when it's on the engine works harder and uses more fuel.

[Ward-Minter]

I would argue with dilligaf  that having a window open will actually give you worse fuel economy.

The resistance from any speeds over about 25mph will seriously reduce  the aerodynamics of the car.

It is for this reason that the most singularly expensive development of a new car is the airflow in wind tunnels.

I may be talking toilet here but seemed to remember physics at school proved this to be the case.

On a slightly related note if you chose not to use aircon make sure you give it a good blast every now and then so pollutants and bugs etc dont form in the pipes.

[dilligaf]

Re Ward Minter reply. I was only useing the term open the window as an example. As far as aerodynamics are concerned it would be better to open a sunroof if fitted on tilt, to reduce the heat in a car which has possibly been parked in the sun. If the vehicle keeps moving there should be enough airflow to keep cool. In traffic queues, shut the windows or sun roof and turn on the air con. The comfort compensates the cost. Do not use air con to cool a moving car, which would be expensive, use it to keep a cooler car cold.

[Carol Anne]

Nothings for nothing. I use the air con summer and winter, (never have condensation problems as the air is dehumidified) On a blistering hot day, what price comfort?