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From: ACAR on 20 Apr 2010 07:20
On Apr 18, 8:11 pm, "Andrew W" <removethis_ajwer...(a)optushome.com.au>
wrote:
> Does using the air conditioner consume much more fuel, especially when
> accelerating?
> And wouldn't one save fuel by installing a vacuum switch that disengages the
> aircon while accelerating?
> Perhaps some newer cars already have this?

If you do a little web searching on your own you'll find car A/C
systems are a lot more sophisticated than you think. All my cars get
their best average MPG in the summer, despite A/C use.
From: hls on 20 Apr 2010 08:57

"ACAR" <dimndsonmywndshld(a)yahoo.com> wrote in message news:02755dcd-

If you do a little web searching on your own you'll find car A/C
systems are a lot more sophisticated than you think. All my cars get
their best average MPG in the summer, despite A/C use.
********
If this is the case (and I would guess you have measured it carefully enough
to be relatively sure of this), are you of the belief that running the AC
gives
you this economy boost? Or is it more likely that summer gasoline blends,
or perhaps average operating conditions (temperature, humidity, etc), cause
the effect?

From: C. E. White on 20 Apr 2010 10:55

"hls" <hls(a)nospam.nix> wrote in message
news:prqdnRcDRrgmOVDWnZ2dnUVZ_qmdnZ2d(a)giganews.com...
>
> "ACAR" <dimndsonmywndshld(a)yahoo.com> wrote in message news:02755dcd-
>
> If you do a little web searching on your own you'll find car A/C
> systems are a lot more sophisticated than you think. All my cars get
> their best average MPG in the summer, despite A/C use.
> ********
> If this is the case (and I would guess you have measured it
> carefully enough
> to be relatively sure of this), are you of the belief that running
> the AC gives
> you this economy boost? Or is it more likely that summer gasoline
> blends,
> or perhaps average operating conditions (temperature, humidity,
> etc), cause
> the effect?

The extra fuel required to operate the A/C is trivial and is easily
masked by the factors you mentioned and many others. Here area few i
can thingk of:

* Car are more fuel efficient when warmed up, so anything that reduces
warm up time will improve fuel economy.
* Rear axle and transmission fluids are less viscous when warm,
resulting in lower gear train losses in the summer.
* Rubber is more flexible when hot, so the tires use less energy to
"flex" when rolling.
* Summer and Winter fuel blends are different, so that can make a
difference.
* You use your headlights more in winter, which like the A/C, requires
additional power.
* Summer driving probably involves less bad weather driving (driving
on snow and wet roads decreases fuel economy).
* Warm air is less dense, slightly lowering air resistance.
* You are more likely to take longer highway trips in warm weather,
biasing your fuel economy more towards the highway mileage.
* Becasue driving conditions are better, commuting probably involves
less stop and go driving in the summer.

Etc. Etc. Etc.

Plus, don't forget most cans run the A/C in the winter when you turn
on the defroster if the outside temeprature is above 40F. So even if
you are not using the A/C...you are.

Ed


From: Sharx35 on 20 Apr 2010 19:24


"C. E. White" <cewhite3(a)mindspring.com> wrote in message
news:hqkf8s$uil$1(a)news.eternal-september.org...
>
> "hls" <hls(a)nospam.nix> wrote in message
> news:prqdnRcDRrgmOVDWnZ2dnUVZ_qmdnZ2d(a)giganews.com...
>>
>> "ACAR" <dimndsonmywndshld(a)yahoo.com> wrote in message news:02755dcd-
>>
>> If you do a little web searching on your own you'll find car A/C
>> systems are a lot more sophisticated than you think. All my cars get
>> their best average MPG in the summer, despite A/C use.
>> ********
>> If this is the case (and I would guess you have measured it carefully
>> enough
>> to be relatively sure of this), are you of the belief that running the AC
>> gives
>> you this economy boost? Or is it more likely that summer gasoline
>> blends,
>> or perhaps average operating conditions (temperature, humidity, etc),
>> cause
>> the effect?
>
> The extra fuel required to operate the A/C is trivial and is easily masked
> by the factors you mentioned and many others. Here area few i can thingk
> of:
>
> * Car are more fuel efficient when warmed up, so anything that reduces
> warm up time will improve fuel economy.
> * Rear axle and transmission fluids are less viscous when warm, resulting
> in lower gear train losses in the summer.
> * Rubber is more flexible when hot, so the tires use less energy to "flex"
> when rolling.
> * Summer and Winter fuel blends are different, so that can make a
> difference.
> * You use your headlights more in winter, which like the A/C, requires
> additional power.
> * Summer driving probably involves less bad weather driving (driving on
> snow and wet roads decreases fuel economy).
> * Warm air is less dense, slightly lowering air resistance.
> * You are more likely to take longer highway trips in warm weather,
> biasing your fuel economy more towards the highway mileage.
> * Becasue driving conditions are better, commuting probably involves less
> stop and go driving in the summer.
>
> Etc. Etc. Etc.
>
> Plus, don't forget most cans run the A/C in the winter when you turn on
> the defroster if the outside temeprature is above 40F. So even if you are
> not using the A/C...you are.
>
> Ed

A lot of good points, Ed. Why anyone would hesitate ONE SECOND before
activating the AC, in the car OR the house, is beyond me. Life is too short
to suffer heat...or cold.


>
From: Leftie on 21 Apr 2010 00:41
Andrew W wrote:
> Does using the air conditioner consume much more fuel, especially when
> accelerating?
> And wouldn't one save fuel by installing a vacuum switch that disengages the
> aircon while accelerating?
> Perhaps some newer cars already have this?
>
>

Yes, yes, and maybe a few. I do it manually, switching the AC off to
accelerate and back on at cruising speed. Don't open the windows wide
instead, though, because that causes as much drag as running the AC with
the windows closed, at highway speeds.
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