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Discussion Starter · #1 ·
Hi All,

I spotted this the other day, and thought with all the topics on fuel consumption it gives a good insight into the effect air-con has on fuel consumption.

The guy is an air conditioning engineer and his thoughts and comments make interesting reading.

Being a Yorkshire man I'm all about saving a few quid.

Anyway enjoy.

http://www.airconditioningforcars.co.uk/ACpage05.htm







Edited by: uncletone
 

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Some more factorsAs well as the outside temp / humidity and indeed the brightness of the sun, effecting how much difference is made to the fuel consumption, the colour of the vehicle also has an impact, White or light cars will absorb less heat from the sun, while dark colours will have a higher impact, so that in all cases this has to be taken into account.
Not an easy exercise to quantify.

But a very interesting article.
 

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Discussion Starter · #3 ·
Totally agree David,

I appreciate that running with your air-con on and along with the factors you pointed out, it does affect the fuel consumption.



I just think for the savings involved, personally I can't be bothered about switching it off at all. This time of year it keeps the windows clear and for me that' s a benefit in itself. Also it stops the seals in the system lubricated helping to prevent a loss of gas which can lead to other issues.



In the Jag which has an all leather interior the effects of air -con can dry the leather out which means as part of the
regular/cleaningschedule, I have to treat the leather and at the start of the winter I end up cleaning and feeding it.



But I do understand why some prefer to switch it off.
 

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I never turn it off. I've long been convinced that the effects on fuel consumption are minimal, but I am aware that the cost of not using the system regularly can be huge with compressors seizing, pipe work and joints perishing etc.
 

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I once had a Renault Megane and was very frugal with the air con.... the first summer the car was out of warranty I went to switch it on and nothing happened (other than a whirring noise) - Renault agreed to go halves on a new unit but it still cost me over £500!! They said it was because it hadn't been used regularly enough. I now keep climate control switched on....Edited by: KateinNotts
 

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In addition it should be noted that having the air con on will cause a slight increase of load on the engine and hence fuel consumption, try turning it on and off when the engine is idling and you'll see the revs move up/down accordingly. It will also marginally impact acceleration, so just prior to max acceleration, for example overtaking, turn off the air con. Also it's worthturning off the air con at least 1 minute prior to parking the car, it gives the air consystem a chanceto run down.
The air con does need using every now and then to help keep the internal parts moving and to help prevent the system getting bad bacteria gathering and causing a smell inside the car when the fan is on.

Any fuel we can save means less pollution and more for future usage and that's always good.
 

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It's climate control (in most of our cars anyway), so it's supposed to be left on all the time. Really the power it takes and the impact on fuel consumption is marginal.
 

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Discussion Starter · #8 ·
Totally agree Andrew,

If I turned mine off prior to any acceleration runs/overtaking by the time I'd done that I would probably have missed the opportunity as it needs the length of the M5 to get going.
 

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Light said:
It will also marginally impact acceleration, so just prior to max acceleration, for example overtaking, turn off the air con.
Most systems disengage the compressor on hard acceleration, the unit in my A2 certainly does.
 

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Discussion Starter · #10 ·
Yep, couldn't agree more with the comments above.

The affect on fuel consumption, in my opinion is minimal against the benefits of leaving it on all the time.

I know "madam" has hers on in the Peugeot all the time and I certainly have it on in the Jag. If I switched it off, I doubt I would notice the increase in power anyway.
 

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uncletone said:
I certainly have it on in the Jag. If I switched it off, I doubt I would notice the increase in power anyway. 
It will only take 3-5bhp in the jag so you wouldn't notice it - we used to own a smart with A/C and would refer to it as the turbo button because it didn't automatically disengage at full throttle; on a hill you'd turn it off and the car would get a new lease of life!
 

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The auto AC (climatronic) does not take so much power as the manual one, so the difference of 1-2 HP will probably not be noticed...If you set it Mono (both zones have same temp), and also at the comfort limit (do not put it to 20 degrees when outside is 35 :))), but at 26), the impact in consumption will be minimal...
On diesel engines you probably will not sense it, maybe will have more impact in petrol engine...
My car had always the AC Auto, set at 24 degrees Celsius in normal weather and 26 at very warm days, the consumption in diesel was almost the same.
I can not say the same thing about manual AC...this one is directly connected to engine (mechanical compressor), and is taking around 4 HP...also the consumption in petrol car increase with 1-1,5 liters at 100km...
 
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