Hybrid Car – More Fun with Less Gas

Question about MPG - Page 4

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Posted by Bob Wilson on August 8, 2006, 5:04 am
 




Ok, a couple of things:

1) Can you do the first mile at 25-30 mph?

This will let you get the engine and systems up to operating
temperature. Thereafter, you'll get much better fuel efficiency.

2) The oil level is OK?

3) About your speeds:


We have some MPG vs MPH data:

http://home.hiwaay.net/~bzwilson/prius/epa.jpg


You control the speed, the MPG follows.


I use pump recepts for my long term average. I find the MFD is best used
for 'tests' or learning how to drive.

Bob Wilson
  

Posted by Miwaku on August 8, 2006, 12:15 pm
 


Thanks,  Bob. I appreciate the effort.


Posted by Steve Pardoe on August 14, 2006, 2:51 pm
 


Good point!  I'm genuinely interested in hearing accurate data for a change.


Trip computers are notoriously inaccurate (erring on the economical side -
which auto manufacturer wouldn't prefer that?).


But over several fillups (say a couple of thousand miles) the total amount
of fuel put in will be valid, and (give or take some slack on the last fill)
should give a fair basis for the math(s) if you record the start and finish
odometer readings.  Then do the math, and see whether you still get 51 mpg,
but I'm guessing the computer will turn out to be significantly optimistic.
As the OP says, it's the _only_ way to get a realistic mpg figure (for any
car).

The Prius is a reasonably economical car, especially in the urban cycle, but
it still ultimately gets _all_ its energy from a gasoline engine, rather
than a diesel, which is what we Europeans have come to know and love.

Steve P




Posted by Bill on August 14, 2006, 3:38 pm
 



I didn't know there was a hybrid diesel on the market.  If you are comparing
the Prius to the conventional diesel then your statement regarding energy
deserves some clarification.  In both cases the energy comes from the engine
HOWEVER the Prius is capable of recovering some of it's own energy whereas
the conventional diesel is not.  Climb a hill with both and an efficient
diesel will use less fuel than an efficient gas engine.  On the other side
of the hill, on the way down, the Prius will recapture some of that energy
and store it in it's battery bank to be used when needed.   When a Prius is
slowing to a stop, it is recovering some of the energy required to get it up
to speed in the first place.  The conventional diesel, unable to recapture
energy, is less efficient overall.

Then, of course, there is the matter of hydrocarbon emissions....  What
Europeans have learned that Americans don't understand is that smaller,
lighter vehicles take less fuel to operate.  The situation in Europe, and
especially in Asia, is remarkably different in another aspect.  Population
density is such that many more people can be served per truck-mile.  When I
lived in what was then West Germany, the country was the size of Minnesota
with a population 1/4 of the U.S. population.  That same population density
made mass transportation economically feasable and, in many cases,
preferable to personal transportation.

Don't get me wrong here.  I don't excuse my fellow Americans for wasting
fuel and emitting hydrocarbons.  It's a national disgrace, worse in the long
run than the unnecessary invasion of Iraq.







Posted by Steve Pardoe on August 14, 2006, 10:10 pm
 


Presuming that enough people continue to think hybrids are the way forward
(I'm not yet convinced), Europe will go for diesel every time.  In many
countries, diesel cars far outnumber gasoline already.  Several
manufacturers who area talking about doing hybrids in Europe are talking
only diesel, rather than gasoline.  However, there are also makers such as
VW who are releasing super-economical (non-hybrid) diesels with very low
emissions and exceptional fuel mileage (aiming for 3 litres per 100km).
It's interesting that in several cases recently the most powerful model in a
maker's range is a diesel - e.g. the VW Touareg, Skoda Fabia, etc.


Of course, that's what the batteries are for (though I have met people who
say that the reason for the Prius's economy is that some of the power is
ultimately "electric", without having thought much about where the
electricity comes from).


Correct.


There are two caveats.  The first is that in normal driving (not in
stop-start traffic) how much time do you actually spend pressing the brake
pedal?  Not much, as a proportion of a journey, unless you are a driver with
exceptionally poor anticipation.  This is evidenced by the very low capacity
of the Prius battery pack, only able to power the car for a few seconds at
full output, which in turn explains why Toyota provided no facility to
charge it from the mains.  There's no point.

Second, lugging the additional mass of the battery pack, electric motor /
generator set, power and temperature control units, etc around all the time
has an impact on economy.


Indeed, dramatically less.  Increased vehicle body mass / engine power
increases secondary items such as transmission, brakes, suspension, and it's
a vicious circle.


In and around London it's the only sensible option.  Millions of people take
the train every day.


..which will bite the US in the bum.


Don't get me started.  Aas a Brit, I'm disgusted that our government has
been going along with it.

Steve P



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