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I've just bought a new Rio 1 1.1 ecodynamic with air trim(aircon) as a business vehicle as the ecodynamic is classed as one of the most economical cars to drive. Now I've been a little disheartened to hear from reviewers that the massive 88 mpg on the base model is impaired to a not so massive 78, though still a good score granted, on my air model. Now, is that based on running the aircon or if I leave it switched off, ie two thirds of the year will I get the better mpg of 88.??? Or iso it something that is changed by merely having the ac unit installed that lowers mpg and raises emissions?
 

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2020 Kia Sorento EX+
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I've just bought a new Rio 1 1.1 ecodynamic with air trim(aircon) as a business vehicle as the ecodynamic is classed as one of the most economical cars to drive. Now I've been a little disheartened to hear from reviewers that the massive 88 mpg on the base model is impaired to a not so massive 78, though still a good score granted, on my air model. Now, is that based on running the aircon or if I leave it switched off, ie two thirds of the year will I get the better mpg of 88.??? Or iso it something that is changed by merely having the ac unit installed that lowers mpg and raises emissions?
running the a/c compressor does suck some mpg, a couple percent i think.
that being said, if you don't use it, it won't suck more fuel.

note: on my car, even if the a/c light isn't on, turns out that the a/c compressor is running most of the time anyway if it thinks it needs to defrost windows, or if i have it on auto mode then a/c runs all the time but the little a/c light does not give any indication that it is running. only way i can tell is that my car makes a bit of a racket when the a/c is running, so i know that it is on even when i don't think it should be.

when i am in auto mode the a/c is on ALL the time, no matter what temp i set, but the light is never on unless i set the temp to "low". in manual mode the a/c comes on any time the car decides that my front window needs defrosting, and as far as i can tell there is no way to turn this "auto defrost while in manual mode" off.

there is always the debate if you use more fuel opening your windows (due to air drag) or using the a/c. lots of opinions, but the one i subscribe to (from mythbusters tv show) is that when you are going slow and there isn't much drag effect, it is better to open your windows. when you are driving closer to highway speeds, drag does become significant, and you are better off closing the windows, reducing drag, and using the a/c to keep you cool.
 

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Discussion Starter #3
Thanks, just couldn't think why just having the ac unit installed would yield a lower 'on paper' mpg. Save maybe a few kilos added weight?
 

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Cerato S Hatch Auto
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Can't give you figures for the 1.1 engine, but my 2 litre cars usually get 2 or 3 less MPG due to the A/C in summer time (35°C).

Don't forget that although the A/C may be "running all the time", it's only sucking a lot of power when the compressor is operating. For comparison, a domestic room A/C will consume 1500 Watts when the compressor is going vs. 150 Watts when just circulating. An auto A/C is probably 2000 Watts for a small car (2 kW).
 

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Can't give you figures for the 1.1 engine, but my 2 litre cars usually get 2 or 3 less MPG due to the A/C in summer time (35°C).

Don't forget that although the A/C may be "running all the time", it's only sucking a lot of power when the compressor is operating. For comparison, a domestic room A/C will consume 1500 Watts when the compressor is going vs. 150 Watts when just circulating. An auto A/C is probably 2000 Watts for a small car (2 kW).
by "running all the time" i literally mean compressor running all the time. doesn't matter what the temperature is set to, what the cabin temp is, or what the outside temp is, or any combination or permutation of all 3, the compressor runs all the time when i am in "auto" setting, even if the heat is on and it isn't humid inside or outside of the car!
so basically, if i am in auto mode, i am consuming 2000 watts all the time, unless i turn off the climate control automatic mode, in which case, what is the point of having it?
i know that the compressor is running because mine makes noise when it is running, when i manually shut the a/c off in manual mode, or turn of climate control all together, the compressor sound goes away.
crazy right?
 
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