km/L or mpg for hybrids and all-electric vehicles are much more dependent
on climate.
Climate and congestion are very important in determining fuel economy for
hybrids and all-electric vehicles. EPA hasn't addressed it properly.
For example, if you are stuck in traffic and the temperature is hot, you
have the AC operating; Therefore you are using energy and fuel for cooling,
along with accessories being used, rather than for moving the vehicle.
Moderate climates will use less energy while hot climates will use more.
Similarly for cold climates where battery efficiency is worse than for warm
climates and heating is needed.
Climate will be much more important in determining fuel economy for
all-electric vehicles.
Stan Doore
----- Original Message -----
From: Bill Potts
To: U.S. Metric Association
Sent: Monday, January 28, 2008 1:19 AM
Subject: [USMA:40255] Re: convenient numerical values
J. Ward wrote: 'As a physicist I would speak in terms of "per meter squared."'
Maybe so (and we had a discussion on this list a few years ago, involving
that same ultimate reduction), but it is something that neither the physicist
nor the layperson can readily visualize (although the physicist can rationalize
its use).
Your comments on average fleet mileage serve to remind us of the need to do a
better job of teaching mathematics. It's the classic case of failure to
recognize that, because the calculation has to be done on the basis of
consumption, rather than range, one must average the reciprocals and then use
the reciprocal of the result. For the car manufacturers to arrive at an
advertised average in any other way should be considered fraud--and prosecuted
as such. And, obviously, Congress should not be so easily fooled by the antics
of a self-serving industry (and should write the formula to be used into the
law).
In the meantime, distance traveled per unit volume (km/L or mpg) tends, I
believe, to be more meaningful to the person doing the traveling and buying the
gas. For that reason, it makes metrication more acceptable to the average
person.
Bill Potts, CMS
Roseville, CA
http://metric1.org [SI Navigator]
----------------------------------------------------------------------------
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of J. Ward
Sent: Sunday, January 27, 2008 20:22
To: U.S. Metric Association
Cc: U.S. Metric Association
Subject: [USMA:40254] Re: convenient numerical values
The biggest disadvantage of km/L is to give a huge loop-hole to auto maker
who sell gas guzzlers. For example, the U.S. government has requirements for
fleet averages in terms of miles/gallon. Imagine I'm an automaker and I want
to sell muscle cars or monster trucks that average 5 miles/gallon. If I can
sell a single 55 mpg economy car for every 5 mpg gas-hog I sell to get a
respectable fleet average of 30 mpg. This misleads the public (and most
Congressmen!) into assuming that the cars sold use the same amount of fuel to
go a given distance as two vehicles that individually average 30 mpg. Nothing
could be further from the truth! In fact, the two vehicles use the same amount
of fuel to go a given distance as two vehicles that individually average 9 mpg.
Now work the same problem in L/100 km. The economy car uses 4.3 L/100 km.
The guzzler uses 47 km/100 L. The fleet average is 26 L/100 km, which
accurately reflects the huge amount of fuel used by the fleet per kilometer
driven. Clearly, Europe is doing a lot better than we are in terms of how they
measure fuel consumption.
Finally, I would add that an SI purist would never use km/L. As a
physicist I would speak in terms of "per meter squared."
Therefore, I prefer L/100 km over km/L, clumsy as it may seem at first
glance.
J.
Bill Potts wrote:
Clearly, km/L is the more rational.
Bill Potts
Roseville, CA
http://metric1.org [SI Navigator]
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Ziser, Jesse
Sent: Sunday, January 27, 2008 17:38
To: U.S. Metric Association
Subject: [USMA:40252] Re: convenient numerical values
--- Pat Naughtin <[EMAIL PROTECTED]> wrote:
On 2008/01/28, at 8:10 AM, <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> wrote:
Deciliter in the denominator is conventional medical practice in
which "convenient numerical values" are considered more valuable
than coherence of units. The same is true for grams and mg in
medical practice.
Gene.
Dear Gene and All,
The expression you use here, 'convenient numerical values' appears
quite often in many different contexts and, it seems to me, that this
is at the expense of an efficient metrication upgrade.
Another example is the change from millibars to hectopascals in
meteorology where the numbers stay the same while the unit name
changes without gaining the benefits of the coherence of the metric
system or the convenience of the 'rule of thousands'. I am sure that
there are many other examples.
I'd like to offer another possible example of violation of the rule of
thousands. I keep seeing L/100 km in fuel efficiency contexts. I also
occasionally see km/L but it appears to be rarer.
km/L is clearly more "thousandy", and also has the debatable advantage of
being "distance per volume" just like MPG. Besides, "L/100 km" seems an
awkward mouthful. Is this really the preferred unit?
I'm thinking about getting metric mileage bumper stickers for my friends and
family (most of whom I'm sure would enthusiastically accept and display
them) and I was wondering if anyone had any other opinions on the km/L
versus L/100 km issue. I've been unable to find much about it online.
Thanks.
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