Question about fuel economy

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Old 18 Apr 2010, 07:11 pm   #1 (permalink)
Andrew W
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Default Question about fuel economy

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?


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Old 18 Apr 2010, 11:17 pm   #2 (permalink)
Sharx35
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Default Re: Question about fuel economy



"Andrew W" <removethis_ajwerner@optushome.com.au> wrote in message
news:4bcb9fb0$0$22779$afc38c87@news.optusnet.com.a u...
> 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?
>


Andrew, who really gives a shit? I'd rather be cool AND comfortable no
matter WHAT the cost.

>

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Old 19 Apr 2010, 04:03 am   #3 (permalink)
dsi1
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Default Re: Question about fuel economy

On 4/18/2010 2:11 PM, 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?
>
>


Using the air conditioner will consume more fuel. I don't know what you
consider "much more." My guess is that it uses a little more fuel. We
used to have a Ford with an AC that shut off under low vac conditions -
boy was that annoying!
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Old 19 Apr 2010, 04:57 am   #4 (permalink)
Sharx35
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Default Re: Question about fuel economy



"dsi1" <dsi1@spamnet.com> wrote in message
news:t%Uyn.76924$iL1.31771@newsfe24.iad...
> On 4/18/2010 2:11 PM, 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?
>>
>>

>
> Using the air conditioner will consume more fuel. I don't know what you
> consider "much more." My guess is that it uses a little more fuel. We used
> to have a Ford with an AC that shut off under low vac conditions - boy was
> that annoying!


Remember the days when vacuum operated windshield wipers would shut down
while climbing hills?


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Old 19 Apr 2010, 06:05 am   #5 (permalink)
dsi1
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Default Re: Question about fuel economy

On 4/18/2010 11:57 PM, Sharx35 wrote:
>
>
> "dsi1" <dsi1@spamnet.com> wrote in message
> news:t%Uyn.76924$iL1.31771@newsfe24.iad...
>> On 4/18/2010 2:11 PM, 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?
>>>
>>>

>>
>> Using the air conditioner will consume more fuel. I don't know what
>> you consider "much more." My guess is that it uses a little more fuel.
>> We used to have a Ford with an AC that shut off under low vac
>> conditions - boy was that annoying!

>
> Remember the days when vacuum operated windshield wipers would shut down
> while climbing hills?


I have heard of vac operated wipers but that was before my time. The
oldest car I've ever had was a 65 Nova. Just lucky, I guess. :-)
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Old 19 Apr 2010, 07:34 am   #6 (permalink)
C. E. White
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Default Re: Question about fuel economy


"Andrew W" <removethis_ajwerner@optushome.com.au> wrote in message
news:4bcb9fb0$0$22779$afc38c87@news.optusnet.com.a u...
> Does using the air conditioner consume much more fuel, especially
> when accelerating?


In theory using the A/C should consume more fuel. In practice, I've
never been able to detect the difference. I keep fuel log books for
all my vehicles. I've looked at fuel consumption by month numerous
times and find that often my lowest average fuel consumption is in the
summer, when A/C usage is the highest. My assumption is that changes
in fuel composition, driving patterns, warm up time, etc., etc.,
totally mask any additional fuel consumption related to A/C usage.

> And wouldn't one save fuel by installing a vacuum switch that
> disengages the aircon while accelerating?
> Perhaps some newer cars already have this?


I think all new cars have the ability to disable the A/C during period
of maximum power requirements. There is no longer a need to use a
vacuum switch for this function. The engine computer can decide to
disengage the A/C compressor only at wide open throttle or some as the
result of other combinations of conditions based on the various sensor
inputs. This is a lot more sophisticated than using a simple vacuum
switch.


Ed


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Old 20 Apr 2010, 06:20 am   #7 (permalink)
ACAR
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Default Re: Question about fuel economy

On Apr 18, 8:11*pm, "Andrew W" <removethis_ajwer...@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.
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Old 20 Apr 2010, 07:57 am   #8 (permalink)
hls
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Default Re: Question about fuel economy


"ACAR" <dimndsonmywndshld@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?

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Old 20 Apr 2010, 09:55 am   #9 (permalink)
C. E. White
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Default Re: Question about fuel economy


"hls" <hls@nospam.nix> wrote in message
newsrqdnRcDRrgmOVDWnZ2dnUVZ_qmdnZ2d@giganews.com ...
>
> "ACAR" <dimndsonmywndshld@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


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Old 20 Apr 2010, 06:24 pm   #10 (permalink)
Sharx35
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Default Re: Question about fuel economy



"C. E. White" <cewhite3@mindspring.com> wrote in message
news:hqkf8s$uil$1@news.eternal-september.org...
>
> "hls" <hls@nospam.nix> wrote in message
> newsrqdnRcDRrgmOVDWnZ2dnUVZ_qmdnZ2d@giganews.com ...
>>
>> "ACAR" <dimndsonmywndshld@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.


>

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