Economy Trivia

[2ndGear]

Re - Black IQ in hot weather - Which uses more fuel – Windows down or Air Con on?

[APS]

Depends on how fast you are going. In general - on motorway use air con. In town windows down.

Having said that - if the car has been standing in the sun I would normally roll the windows down for the first few minutes to vent most of the hot ait out and then keep the air con on all the time.

The engine size does also make a difference. On my 2.0 diesel corolla I have never been able to see any difference in fuel economy with air con on during the 165k miles I've driven it.

But on a smaller petrol engine this may be more noticeable.

[2ndGear]

Thank you for the reply. I haven’t found any data on Air-con fuel consumption per hour, but your sound advice is welcome. I have noticed the variation of fuel usage between IQ owners is considerable.

[rowbot]

I read somewhere that on average, air-con reduces mpg by 1.

[gizzard]

Its the 50/50 rule I think.

Under 50 windows, over 50 aircon.

There was a Mythbusters program where they appeared to have proved it.

[bokkie]

Its the 50/50 rule I think.

Under 50 windows, over 50 aircon.

There was a Mythbusters program where they appeared to have proved it.

The area that releases the most heat in a car is the top of the dash. Once you've vented most of that then aircon can do its job better. Until then, feel the heat of the dash by hand to get an idea how it's cooling with the window(s) open. What I like about any aircon is that there's no better or quicker way to demist a windscreen that's pregnant with condensation! :)