Influence of window opening vs. A/C use on fuel economy
09-06-2006 | 08:07 PM
#16
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
Great job. Please test next without the luggage on top and replace 4
cylinder with 6.
"Gordon McGrew" <gRmEcMgOrVeEw@mindspring.com> wrote in message
news:ml3uf21mpn3tgt45va1s5v7tch8u4un5p2@4ax.com...
>
>
> It has become popular lately to claim that turning on A/C uses less
> fuel than opening windows. On a recent round trip to Kansas I used my
> handy Scan Gauge to check milage under different operating conditions.
> (What else is there to do driving across Missouri and Kansas?)
>
> I checked the calculated fuel economy over approximate ten mile
> segments on each tank of fuel. I used the cruise control and the
> calibrated Scan Gauge mph measurements. Usually I could go the whole
> ten miles without touching the gas or brake. I tried to be as
> consistent as possible.
>
> For open windows, I started out rolling them all the way down but
> after a couple segments of that, I decided that no one could stand the
> tornado effect for long distances so I tried various partial open
> positions which improved ventilation without being punishing.
> Generally this was the rears open 4 inches and the fronts either
> closed or open 3 inches.
>
> The vehicle, unfortunately, was not typical for most drivers: 1998
> Odyssey 4 cylinder with a Thule car-top cargo box. Newer A/C systems
> and less drag-challenged vehicles may yield different results, but
> here goes...
>
>
> Test 1 8/31/06 76 mph I35 Southbound Hilly
> 22.8 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 4 19.83 100
> Off Full Open 2 19.45 98
> Off Part Open 2 18.90 95
> On Closed 4 18.24 92
>
>
> Test 2 9/4/06 75 mph I35 Northbound Hilly
> 19.7 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 5 21.62 100
> Off Part Open 3 21.27 98
> On Closed 1 20.90 97
>
>
> Test 3 9/5/06 75 mph I35 Northbound Hilly
> 23.4 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 3 20.43 100
> Off Part Open 2 20.65 101
> On Closed 3 19.27 94
>
>
> Test 4 9/5/06 73 mph I55 Northbound Flat
> 21.6 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 6 22.22 100
> Off Part Open 5 21.68 98
> On Closed 5 20.82 94
>
>
> Overall, weighted by number of segments relative to windows up, A/C
> off, fuel efficiency was:
>
> Windows open 98%
> A/C on 94%
>
> In this test, turning on the A/C cost three times as much fuel as
> opening the windows. There was no indication that it made any
> difference whether the windows were wide open, rears down 4 inches or
> front and rear both down 3 - 4 inches, but there was limited testing
> of this, and the effect was small in any event.
>
> As noted before the vehicle may not be typical, but these were the
> results. One further point of interest; shortly after I started one
> segment I came upon a speed reduced work zone. I didn't use the
> segment in the above calculations but I noted that average speed was
> 63 mph and average fuel consumption was 26.4 mpg. It appears that the
> difference between going 60 and going 75 was about 4 mpg.
>
>
>
>
>
cylinder with 6.
"Gordon McGrew" <gRmEcMgOrVeEw@mindspring.com> wrote in message
news:ml3uf21mpn3tgt45va1s5v7tch8u4un5p2@4ax.com...
>
>
> It has become popular lately to claim that turning on A/C uses less
> fuel than opening windows. On a recent round trip to Kansas I used my
> handy Scan Gauge to check milage under different operating conditions.
> (What else is there to do driving across Missouri and Kansas?)
>
> I checked the calculated fuel economy over approximate ten mile
> segments on each tank of fuel. I used the cruise control and the
> calibrated Scan Gauge mph measurements. Usually I could go the whole
> ten miles without touching the gas or brake. I tried to be as
> consistent as possible.
>
> For open windows, I started out rolling them all the way down but
> after a couple segments of that, I decided that no one could stand the
> tornado effect for long distances so I tried various partial open
> positions which improved ventilation without being punishing.
> Generally this was the rears open 4 inches and the fronts either
> closed or open 3 inches.
>
> The vehicle, unfortunately, was not typical for most drivers: 1998
> Odyssey 4 cylinder with a Thule car-top cargo box. Newer A/C systems
> and less drag-challenged vehicles may yield different results, but
> here goes...
>
>
> Test 1 8/31/06 76 mph I35 Southbound Hilly
> 22.8 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 4 19.83 100
> Off Full Open 2 19.45 98
> Off Part Open 2 18.90 95
> On Closed 4 18.24 92
>
>
> Test 2 9/4/06 75 mph I35 Northbound Hilly
> 19.7 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 5 21.62 100
> Off Part Open 3 21.27 98
> On Closed 1 20.90 97
>
>
> Test 3 9/5/06 75 mph I35 Northbound Hilly
> 23.4 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 3 20.43 100
> Off Part Open 2 20.65 101
> On Closed 3 19.27 94
>
>
> Test 4 9/5/06 73 mph I55 Northbound Flat
> 21.6 mpg overall (measured)
>
> A/C Windows # Segments Ave. MPG Relative MPG
> Off Closed 6 22.22 100
> Off Part Open 5 21.68 98
> On Closed 5 20.82 94
>
>
> Overall, weighted by number of segments relative to windows up, A/C
> off, fuel efficiency was:
>
> Windows open 98%
> A/C on 94%
>
> In this test, turning on the A/C cost three times as much fuel as
> opening the windows. There was no indication that it made any
> difference whether the windows were wide open, rears down 4 inches or
> front and rear both down 3 - 4 inches, but there was limited testing
> of this, and the effect was small in any event.
>
> As noted before the vehicle may not be typical, but these were the
> results. One further point of interest; shortly after I started one
> segment I came upon a speed reduced work zone. I didn't use the
> segment in the above calculations but I noted that average speed was
> 63 mph and average fuel consumption was 26.4 mpg. It appears that the
> difference between going 60 and going 75 was about 4 mpg.
>
>
>
>
>
09-06-2006 | 08:43 PM
#20
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
A/C is essentially a "minutes per gallon" question while driving represents
more of a "miles per gallon" cost. I think it's certain that at low speeds
the efficiency is better with the windows open and A/C off while at high
speeds the opposite is true. Where that changeover point is undoubtedly
varies widely from model to model, and the "high speed" regime may start
above the speed limit for many cars.
When the Mythbusters ran their test they used SUVs which drank a lot of
gasoline anyway and probably didn't suffer much when the windows were open.
In addition, the speed was so low A/C would be a clear loser.
Mike
more of a "miles per gallon" cost. I think it's certain that at low speeds
the efficiency is better with the windows open and A/C off while at high
speeds the opposite is true. Where that changeover point is undoubtedly
varies widely from model to model, and the "high speed" regime may start
above the speed limit for many cars.
When the Mythbusters ran their test they used SUVs which drank a lot of
gasoline anyway and probably didn't suffer much when the windows were open.
In addition, the speed was so low A/C would be a clear loser.
Mike
09-06-2006 | 08:43 PM
#21
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
A/C is essentially a "minutes per gallon" question while driving represents
more of a "miles per gallon" cost. I think it's certain that at low speeds
the efficiency is better with the windows open and A/C off while at high
speeds the opposite is true. Where that changeover point is undoubtedly
varies widely from model to model, and the "high speed" regime may start
above the speed limit for many cars.
When the Mythbusters ran their test they used SUVs which drank a lot of
gasoline anyway and probably didn't suffer much when the windows were open.
In addition, the speed was so low A/C would be a clear loser.
Mike
more of a "miles per gallon" cost. I think it's certain that at low speeds
the efficiency is better with the windows open and A/C off while at high
speeds the opposite is true. Where that changeover point is undoubtedly
varies widely from model to model, and the "high speed" regime may start
above the speed limit for many cars.
When the Mythbusters ran their test they used SUVs which drank a lot of
gasoline anyway and probably didn't suffer much when the windows were open.
In addition, the speed was so low A/C would be a clear loser.
Mike
09-06-2006 | 08:43 PM
#22
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
A/C is essentially a "minutes per gallon" question while driving represents
more of a "miles per gallon" cost. I think it's certain that at low speeds
the efficiency is better with the windows open and A/C off while at high
speeds the opposite is true. Where that changeover point is undoubtedly
varies widely from model to model, and the "high speed" regime may start
above the speed limit for many cars.
When the Mythbusters ran their test they used SUVs which drank a lot of
gasoline anyway and probably didn't suffer much when the windows were open.
In addition, the speed was so low A/C would be a clear loser.
Mike
more of a "miles per gallon" cost. I think it's certain that at low speeds
the efficiency is better with the windows open and A/C off while at high
speeds the opposite is true. Where that changeover point is undoubtedly
varies widely from model to model, and the "high speed" regime may start
above the speed limit for many cars.
When the Mythbusters ran their test they used SUVs which drank a lot of
gasoline anyway and probably didn't suffer much when the windows were open.
In addition, the speed was so low A/C would be a clear loser.
Mike
09-06-2006 | 09:06 PM
#26
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Let me guess - you're not married?
-- R Flowers
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Let me guess - you're not married?
-- R Flowers
09-06-2006 | 09:06 PM
#27
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Let me guess - you're not married?
-- R Flowers
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Let me guess - you're not married?
-- R Flowers
09-06-2006 | 09:06 PM
#28
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Let me guess - you're not married?
-- R Flowers
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Let me guess - you're not married?
-- R Flowers
09-06-2006 | 09:39 PM
#29
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
Nope. Just particular.
Spdloader
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Spdloader
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
09-06-2006 | 09:39 PM
#30
Guest
Posts: n/a
Re: Influence of window opening vs. A/C use on fuel economy
Nope. Just particular.
Spdloader
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>
Spdloader
"Elmo P. Shagnasty" <elmop@nastydesigns.com> wrote in message
news:elmop-AF9CAB.20513706092006@nntp3.usenetserver.com...
> In article <fLILg.6713$Md4.6672@tornado.southeast.rr.com>,
> "Spdloader" <askforit@nospam.triad.rr.com> wrote:
>
>> Windows down messes up my wife's hair.
>
> Big haired wife?
>