[AlanHo]

The evaporator in the aircon failed in my car 6 weeks ago and I am still awaiting the repair.  Spares are on back order.

The timing was unfortunate because it happened 2 days before we were to go on holiday during the heat wave -  the heat in the car was cruel and we did 800 miles in it during the 7 day holiday. It reminded me of my younger days when cars didn't have aircon - you drove with the windows open and a hand in the slipstream trying to encourage a draught of air through the car.

The other side of the coin was the car averaged 71.2 mpg (4.0 l/100km) during the holiday - for such a holiday with long journeys it would normally be 65.6 mpg (4.3 l/100km) which is a difference of 9%.  Some of the improvement could be attributable to the constant very hot weather - but now we are back at home with cooler weather and only local journeys it is hovering around 64 mpg (4.4 l/100km) instead of the usual 59 mpg (4.8 l/100km)

I tend to leave the aircon on auto all the time. From now on I will only use it when absolutely necessary, in order to save on petrol.

[Greyhound]

You could put the aircon ON when decending hills to increase engine braking without increasing fuel consumption.
I had a rental car once where I had to turn the aircon OFF when turning through gaps in oncoming traffic and when climbing steep hills. It was not the most powerful of engines, so it was either that or tell the passengers to get out of the car to facilitate any notion of rapid motion.  

[Shambles]

I will only use it when absolutely necessary, in order to save on petrol.

I'd be surprised if your compressor wasn't electric.  Mine is.

[AlanHo]

I will only use it when absolutely necessary, in order to save on petrol.

I'd be surprised if your compressor wasn't electric.  Mine is.

My car has a conventional refrigerant  system comprising a compressor - condenser (heat exchanger) and evaporator. The evaporator is mounted inside the car under the dash which necessitates the removal of the dashboard etc to get at it.

This is the circuit  How Does A Car Air Conditioning System Work? [2022 Guide].

In my car the evaporator is leaking and must be replaced. An expensive warranty job. Its good my car has a 7 year warranty - it is 5 years and 5 months old.

I am in the process of swapping the car for a 2021 model  Niro which has more bells and whistles and has a 7 year warranty . The 2022 Niro is now available and KIA were left with 57 previous model cars in a compound and selling them at a no-brainer price. It has the same controls as my present car and requires no great learning curve. The new 2022 Niro - like many cars today - is controlled via a rotary selector and touch screen to use the radio, air con, media player , sat nav etc.  I think it is dangerous when driving to have to use a touch screen to alter such things as the cabin temperature etc and thus didn't want the latest model. Not only that my wife prefers a button or knob to play with.


The dealer has the evaporator on order - but will take the car as part Exch for the new one and repair it before selling it on.

[Lorian]

Leave it on  - its not worth worrying about.

[Bob.W]

FWIW I found a similar AC vs non-AC fuel consumption on a recent road trip to Sydney. On way down the ~600km trip in largely 110km/hr zones got 5.0L/100km - day was cool so AC was not used. On way back it was hot - AC on nearly entire way, approx 7c below the ambient temps outside - averaged 5.4L/100km for that section of the trip.

Is a diesel PD - astonishing that a little petrol is doing 4L/100km - how very unfair with our horrible diesel prices - currently $2.20/L in our region!