Why you should never buy a car without a tachometer

On Sun, 18 Sep 2005 22:29:43 GMT, "C. E. White"
> wrote:

>
>"Bill Funk" > wrote in message
.. .
>
>> Well, the fact remains that he's wrong.
>> It may be that the article was dumbed down to make a point, but the
>> answer is still wrong.
>
>I think it was a conservative generalization. The only "good" data I have
>seen on the subject is at
>http://cta.ornl.gov/data/tedb24/Spre.../Table4_25.xls . For the nine
>cars in this study, the average decrease in fuel economy for each 5 mph
>incremental increase in speed above 55 mph was 1.9 mpg. There was a large
>variation between the cars, and one car (a 1997 Toyota Celica) actually got
>better mileage at 60 and 65 than at 55 - although its best mileage was at 25
>mph. None of the car evaluated got better mileage at 70 than at 55. The best
>average speed for the nine cars as a group was at 50 mph and 55 mph (same
>average at those speeds).
>
>Ed
>
I understand what you're saying.

Experts shouldn't make conservative generalizations. It kinda goes
against the whole idea of being quoted as an expert. Experts aren't
supposed to make wrong statements, which this one did.

--
Bill Funk
Replace "g" with "a"
funktionality.blogspot.com

Bill Funk wrote:
> On Sun, 18 Sep 2005 22:29:43 GMT, "C. E. White"
> > wrote:
>
> >
> >"Bill Funk" > wrote in message
> .. .
> >
> >> Well, the fact remains that he's wrong.
> >> It may be that the article was dumbed down to make a point, but the
> >> answer is still wrong.
> >
> >I think it was a conservative generalization. The only "good" data I have
> >seen on the subject is at
> >http://cta.ornl.gov/data/tedb24/Spre.../Table4_25.xls . For the nine
> >cars in this study, the average decrease in fuel economy for each 5 mph
> >incremental increase in speed above 55 mph was 1.9 mpg. There was a large
> >variation between the cars, and one car (a 1997 Toyota Celica) actually got
> >better mileage at 60 and 65 than at 55 - although its best mileage was at 25
> >mph. None of the car evaluated got better mileage at 70 than at 55. The best
> >average speed for the nine cars as a group was at 50 mph and 55 mph (same
> >average at those speeds).
> >
> >Ed
> >
> I understand what you're saying.
>
> Experts shouldn't make conservative generalizations. It kinda goes
> against the whole idea of being quoted as an expert. Experts aren't
> supposed to make wrong statements, which this one did.
>
> --
> Bill Funk
> Replace "g" with "a"
> funktionality.blogspot.com

That was my impression (too broad a brush) when I first read it. Even
his hedge
"average car" didn't cut it for me. His point of 'speed costs' remains
correct though.

Harry K

"Harry K" > wrote in message
ups.com...

> That was my impression (too broad a brush) when I first read it. Even
> his hedge
> "average car" didn't cut it for me. His point of 'speed costs' remains
> correct though.

Maybe he was repeating the EPA/Government Fuel Economy party line? If you
look at the graph at http://www.fueleconomy.gov/feg/driveHabits.shtml it
shows fuel economy decreasing from around 30 mpg at 55 mph to around 24 mpg
at 75 mph - a decrease of 1.5 mpg for each 5 mph incremental increase in
speed. They also include the caveat -"While each vehicle reaches its optimal
fuel economy at a different speed (or range of speeds)...."

I don't see any way an expert could make a statement for every possible car,
so maybe he was just picking the most credible source (at least in his
opinion) he could find. My Expedition comes close to agreeing with this
particular estimate. As best I can tell my Expedition will average close to
20 at a steady state 55. At 75 that drops to around 15 - a 1.25 mpg drop for
each 5 mph increment above 55. I think my old F150 is about the same. I
rarely drive it on the highway any more. But back when the speed limits were
a uniform 55, and I drove around 60, I could average 20 mpg on a trip from
my farm to Raleigh and back (150 miles). Since they raised the speed limits
to 65 or 70 on the major parts of the trip, the F150 won't average 15.

Ed