Fuel economy myths

In article <4706c2c7$0$1547$9a6e19ea@unlimited.newshosting.co m>,
Brent <none@no.com> wrote:

> I've had 13 (I think) GM's, and the seat was never far enough back for
> me. Japanese cars seem to use the internal space better, I have no other
> explanation.

You must have had cars from a different GM than me!
My Japanese Datsun 510s had adequate driver space for me,
but the more recent low end Japanese cars don't.
No it's not my extra 20 lbs that is the problem.

In article <47070B4A.44004113@cac.net>, phil <dbrider@cac.net> wrote:

> slowing down to 55 will do the most to conserve fuel
> i just read a study about mileage and cars,suv's are at the most
> efficient at 55mph regardless of what brand they are. between 30 mph and
> 50 the cars consume more as well as over 60 to 90 mph seems 55 is the
> sweet spot so it's no mistake that mileage is rated at that speed
> detroit will never become competitive until the million dollar bonuses
> stop for the executives and that money is reinvested back into the
> companies

I haven't seen any comparative figures on speed vs mileage,
but I'm sure the most efficient speed for higher boxy vehicles (SUV &
truck) is lower than for lower better streamlined vehicles (cars)

In article <UeENi.367$LD2.225@newssvr17.news.>,
"Edwin Pawlowski" <esp@snet.net> wrote:

> I've found that to be true on my own cars that have the instant readout for
> mileage. Repeated runs over the same piece of road at different speeds on
> my way to work.
>
> Problem is, you can't do it voluntarily by yourself. It is downright
> dangerous to drive at 55 while everyone else is doing 70 or above. Nor can
> I drive a car at 55 on the open road when both the car and highway are built
> to sustain much higher speeds.

The instant readout method is a bit questionable. My wife's Sebring has
it and I've watched it, but you can get a much better comparison of mpg
at different speeds by viewing the mileage over a reasonable distance.

Different cars designs vary as well. My wife's 2001 2.7L Sebring drops
it's mileage off faster at higher speeds than my 3.3L Concorde.
Both get the same mileage at 60mph, but the 3.3L Concorde is better than
the Sebring at 70mph.
I've also noticed this with a few rental 2.7L Intrepids.

I keep track of all our mileage so I have lots of real data on actual
trips as well as urban mileage when the Sebring is slightly better than
the Concorde.
Since I don't travel steady highway speeds at lower than 60mph, I have
no lower speed comparisons. The figures I have are at 60, 65 and 70
mph.

who wrote:
> In article <4706c2c7$0$1547$9a6e19ea@unlimited.newshosting.co m>,
> Brent <none@no.com> wrote:
>
>> I've had 13 (I think) GM's, and the seat was never far enough back for
>> me. Japanese cars seem to use the internal space better, I have no other
>> explanation.
>
> You must have had cars from a different GM than me!
> My Japanese Datsun 510s had adequate driver space for me,
> but the more recent low end Japanese cars don't.
> No it's not my extra 20 lbs that is the problem.

I do second that. Like I said, the crown vics seats just don't seem to
go back all the way, now the models with the more bucket style seat do,
but i'm not sure why. (Maybe just hte design of the seat).

The half tons are fine, as the seat is higher to begin with...

<clare at snyder.on.ca> wrote in message
news:ktggg3dccgsher8q1ep147s208gbutn95a@...
> On Sat, 6 Oct 2007 19:59:19 -0400, "Mike Marlow"
> <mmarlowREMOVE@alltel.net> wrote:
>
>>>
>>> Gas here regularly drops from about $ 1.14 per liter to $.94, and
>>> occaisionally (but not lately) $.87.
>>>
>>> When the reserves gut too high, the price drops. For any excuse at
>>> all, it goes up.
>>
>>Correct - but it's hovering around a consistent price. That's not a
>>plummet
>>as the OP stated.
>
>
> That's a drop of over 1.05 per US gallon overnight.
>

If you see prices fluctuate over $1.00 per gallon (or the metric equivalent)
overnight, I'd suggest you live in a unique economy.

--

-Mike-
mmarlowREMOVE@alltel.net

the cars on the autobahn would also see the optimum efficient operation at 55
mph according to what i was reading like you said the law of physics applying
here
the magic number of 55 is used because of the optimum efficient operation and
it was studied long and hard by the epa and gm before that figure was picked
as a standard
setting the speed limit to 55 would also create a gasoline inventory excess
that would back up the refineries so much so
that the winter and summer blend refining schedule would interfere with the
season blending, they now have to use by epa law.
it would effectively shut them down and they would have to give gas away to
make room for the next blend coming in
that is one reason why we see gas prices drop before summer and before winter
so they can make room for the new blends
i have a customer who works for marathon oil a higher up exec. and those are
his words to me as he hands me a gas card as a tip instead of cash
i drive a rt dalota and use the eway and i drive 55 to help my cut fuel bill
and see folks driving by me so i am not stuck in those wolf paks of cars so i
get less stone chips too

Bill Putney wrote:

> phil wrote:
>
> > slowing down to 55 will do the most to conserve fuel
> > i just read a study about mileage and cars,suv's are at the most
> > efficient at 55mph regardless of what brand they are. between 30 mph and
> > 50 the cars consume more as well as over 60 to 90 mph seems 55 is the
> > sweet spot so it's no mistake that mileage is rated at that speed...
>
> Which is the cause and which is the effect? Are official mileage
> figures done at 55 mph because that is a fixed law of physics that that
> is the optimum (fuel mileage) speed for a wheeled vehicle. *OR* is 55
> mph optimized by the manufacturers for fuel mileage because that is the
> speed at which the law arbitrarily says they have to be measuered at?
>
> I know all about the square laws of wind resistance and all that, but I
> have a hard time believing that 55 mph is the optimum speed by a fixed
> law of physics and not an arbitrary design parameter. Things like this
> get ingrained in the culture to the point that it starts being treated
> as if it were a fixed natural law instead of some arbitrary phenomenon
> created by legislation.
>
> I submit that if the mileage measurements were required to be done at,
> say, 65 mph, lo and behold, within two vehicle design generations you'd
> find studies that proved that 65 mph was the magical optimum fuel
> mileage speed. I'm not saying let's change the official measurement
> speed to 65 mph, but let's be careful to not make the "55 mph is the
> optimum fuel economy speed" an irrefutable law of physics.
>
> Question: Would a study of all cars designed for use on the Autobahn
> also show that opitimum fuel mileage speed is 55 mph?
>
> Bill Putney
> (To reply by e-mail, replace the last letter of the alphabet in my
> address with the letter 'x')

Ted Mittelstaedt wrote:
> "Bill Putney" <bptn@kinez.net> wrote in message
> news:5mpbqtFepcpsU1@mid....

>>Which is the cause and which is the effect? Are official mileage
>>figures done at 55 mph because that is a fixed law of physics that that
>>is the optimum (fuel mileage) speed for a wheeled vehicle.
>
>
> Actually Bill I think that 55mph really is the "sweet spot" for a NON-wind
> optimized
> vehicle.
>
> I ride a motorcycle quite frequently that has NO faring (Honda CB750 if
> anyone cares)
> with an upright riding posture. (it's the most comfortable)
>
> I can feel force on my arms increase as speed increases. However, it is NOT
> linear. Up until about 55 you can barely feel it. The faster I go beyond
> this the
> force really does build up very quickly, even going an additional 5 Mph.
> Normally
> I cruise at 65-70. Other bikers in the M/C forums have noted the same
> thing.

I suspect that it has to do with other things, such as there's some
threshold that you start approaching some force threshold beyond which
your arms have trouble resisting on a sustained basis with the force
increasing by the square of the speed (I think) - to the human mind that
threshold appears as some magic switch point. To someone with slightly
stronger arms, the square law increase in wind force is going to make
that threshold appear at some higher but approximately the same speed,
so when the two people talk, they're going to agree that at around 55
mph, things "really" change.

Not sure of the validity of comparing an arm to a car body anyway.
There's no question that some cars are more efficient at speeds higher
than 55 - as posted by some here. I think you have fallen into the
exact trap I was warning about of making a law of physics about the
so-called 55 mph sweet spot. Wind resistance felt on a human arm on a
motorcycle is not very convincing to me. Watching fuel mileage readouts
at different speeds in different (varying degrees of streamlining and
gearing) vehicles is more convincing.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

philthy wrote:

> the cars on the autobahn would also see the optimum efficient operation at 55
> mph according to what i was reading like you said the law of physics applying
> here
> the magic number of 55 is used because of the optimum efficient operation and
> it was studied long and hard by the epa and gm before that figure was picked
> as a standard

You know it makes no sense at all. Some cars are absolutely more
efficient at higher speeds than 55 mph. What that says is that the
optimum speed can be designed into the vehicle by body design and
gearing, not to mention engine design (cams, intake tuning, etc.) and
ignition tuning curves.

Some cars absolutely get better mileage at higher speeds than others.
That's the starting point for my argument (that optimum speed for fuel
mileage can be designed in and that 55 mph is not dictated by the laws
of physics as the inherent optimum speed).

> setting the speed limit to 55 would also create a gasoline inventory excess
> that would back up the refineries so much so
> that the winter and summer blend refining schedule would interfere with the
> season blending, they now have to use by epa law.
> it would effectively shut them down and they would have to give gas away to
> make room for the next blend coming in
> that is one reason why we see gas prices drop before summer and before winter
> so they can make room for the new blends
> i have a customer who works for marathon oil a higher up exec. and those are
> his words to me as he hands me a gas card as a tip instead of cash
> i drive a rt dalota and use the eway and i drive 55 to help my cut fuel bill
> and see folks driving by me so i am not stuck in those wolf paks of cars so i
> get less stone chips too
>
> Bill Putney wrote:
>
>
>>phil wrote:
>>
>>
>>>slowing down to 55 will do the most to conserve fuel
>>>i just read a study about mileage and cars,suv's are at the most
>>>efficient at 55mph regardless of what brand they are. between 30 mph and
>>>50 the cars consume more as well as over 60 to 90 mph seems 55 is the
>>>sweet spot so it's no mistake that mileage is rated at that speed...
>>
>>Which is the cause and which is the effect? Are official mileage
>>figures done at 55 mph because that is a fixed law of physics that that
>>is the optimum (fuel mileage) speed for a wheeled vehicle. *OR* is 55
>>mph optimized by the manufacturers for fuel mileage because that is the
>>speed at which the law arbitrarily says they have to be measuered at?
>>
>>I know all about the square laws of wind resistance and all that, but I
>>have a hard time believing that 55 mph is the optimum speed by a fixed
>>law of physics and not an arbitrary design parameter. Things like this
>>get ingrained in the culture to the point that it starts being treated
>>as if it were a fixed natural law instead of some arbitrary phenomenon
>>created by legislation.
>>
>>I submit that if the mileage measurements were required to be done at,
>>say, 65 mph, lo and behold, within two vehicle design generations you'd
>>find studies that proved that 65 mph was the magical optimum fuel
>>mileage speed. I'm not saying let's change the official measurement
>>speed to 65 mph, but let's be careful to not make the "55 mph is the
>>optimum fuel economy speed" an irrefutable law of physics.
>>
>>Question: Would a study of all cars designed for use on the Autobahn
>>also show that opitimum fuel mileage speed is 55 mph?
>>
>>Bill Putney
>>(To reply by e-mail, replace the last letter of the alphabet in my
>>address with the letter 'x')
>
>

Gary L. Burnore wrote:

> On Sun, 07 Oct 2007 10:42:13 -0400, Bill Putney <bptn@kinez.net>
> wrote:

>>Wind resistance felt on a human arm on a motorcycle is not very convincing to me.
>>Watching fuel mileage readouts at different speeds in different
>>(varying degrees of streamlining and gearing) vehicles is more convincing.
>
>
> It actually helps to prove your point. If you're riding at 55 into a
> 20 mph wind, the "feeling" should be different than if you're riding
> WITH said 20mph wind.

True.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

Bill Putney <bptn@kinez.net> wrote in
news:5msaafFevvihU1@mid.:

> philthy wrote:
>
>> the cars on the autobahn would also see the optimum efficient
>> operation at 55 mph according to what i was reading like you said the
>> law of physics applying here
>> the magic number of 55 is used because of the optimum efficient
>> operation and it was studied long and hard by the epa and gm before
>> that figure was picked as a standard
>
> You know it makes no sense at all. Some cars are absolutely more
> efficient at higher speeds than 55 mph. What that says is that the
> optimum speed can be designed into the vehicle by body design and
> gearing, not to mention engine design (cams, intake tuning, etc.) and
> ignition tuning curves.
>
> Some cars absolutely get better mileage at higher speeds than others.
> That's the starting point for my argument (that optimum speed for fuel
> mileage can be designed in and that 55 mph is not dictated by the laws
> of physics as the inherent optimum speed).
>
>> setting the speed limit to 55 would also create a gasoline inventory
>> excess that would back up the refineries so much so
>> that the winter and summer blend refining schedule would interfere
>> with the season blending, they now have to use by epa law.
>> it would effectively shut them down and they would have to give gas
>> away to make room for the next blend coming in
>> that is one reason why we see gas prices drop before summer and
>> before winter so they can make room for the new blends
>> i have a customer who works for marathon oil a higher up exec. and
>> those are his words to me as he hands me a gas card as a tip instead
>> of cash i drive a rt dalota and use the eway and i drive 55 to help
>> my cut fuel bill and see folks driving by me so i am not stuck in
>> those wolf paks of cars so i get less stone chips too
>>
>> Bill Putney wrote:
>>
>>
>>>phil wrote:
>>>
>>>
>>>>slowing down to 55 will do the most to conserve fuel
>>>>i just read a study about mileage and cars,suv's are at the most
>>>>efficient at 55mph regardless of what brand they are. between 30 mph
>>>>and 50 the cars consume more as well as over 60 to 90 mph seems 55
>>>>is the sweet spot so it's no mistake that mileage is rated at that
>>>>speed...
>>>
>>>Which is the cause and which is the effect? Are official mileage
>>>figures done at 55 mph because that is a fixed law of physics that
>>>that is the optimum (fuel mileage) speed for a wheeled vehicle. *OR*
>>>is 55 mph optimized by the manufacturers for fuel mileage because
>>>that is the speed at which the law arbitrarily says they have to be
>>>measuered at?
>>>
>>>I know all about the square laws of wind resistance and all that, but
>>>I have a hard time believing that 55 mph is the optimum speed by a
>>>fixed law of physics and not an arbitrary design parameter. Things
>>>like this get ingrained in the culture to the point that it starts
>>>being treated as if it were a fixed natural law instead of some
>>>arbitrary phenomenon created by legislation.
>>>
>>>I submit that if the mileage measurements were required to be done
>>>at, say, 65 mph, lo and behold, within two vehicle design generations
>>>you'd find studies that proved that 65 mph was the magical optimum
>>>fuel mileage speed. I'm not saying let's change the official
>>>measurement speed to 65 mph, but let's be careful to not make the "55
>>>mph is the optimum fuel economy speed" an irrefutable law of physics.
>>>
>>>Question: Would a study of all cars designed for use on the Autobahn
>>>also show that opitimum fuel mileage speed is 55 mph?
>>>
>>>Bill Putney
>>>(To reply by e-mail, replace the last letter of the alphabet in my
>>>address with the letter 'x')
>>
>>
>

It really doesn`t matter how slippery the body (unless someone comes up
with some magic to drop below appx 3.0 which is the current norm, as soon
as you go fast enough to creat a measureable wind resistance from that
point ultimate efficiency will drop off. No amount of gearing will increase
it at that point, unless you drop weight or increase efficieny of the power
plant or drive train losses. If you vechiel is getting better milage at
above 55 than at or below it, it is comprimised in one other department and
could do better. The laws of physics can not be changed only the paramaters
varied. KB

--
Thunder Snake #9
"Protect" your rights or "lose" them.