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surface of the road

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Posted by king on July 6, 2008, 7:38 am
Last Thursday I got my new Prius (the "standard" one).
I'm extremely happy with it. It drives like a limo.

Yesterday I drove my first 500 km from Eindhoven (Netherlands) to the north
of France (Lille).
I was not focussing on the MPG. But after a day of shopping I was tired and
decided to drive back calmly and set the cruisecontrol to 100km/hr  (60 MPH)

In Belgium the highways are a bit bumpier and the surface is not as smooth
as we have them in Holland just across the border.
I noticed the following:

In Belgium I got an average 5,2 l/km ( 45,3 MPG) and when I crossed the
border and the surface of the road turned smooth it showed an immediate
improvement to 4,7 l/km. (50,1 MPG). Still driving on cruisecontrol and no
difference in driving behaviour.

If just by paving the roads properly we can already save 10% instantly on
CO2 emissions and petrol consumption this is somthing to think about.

Do some of you experience the same?


Posted by Mr. G on July 6, 2008, 7:54 pm
(axelvanderkruk@telfort.nl) says...

I never had the situation where I was driving on bumpy roads for a long
stretch, and then on smooth to make the direct comparison, so your
experience is an excellent illustration of how the road conditions
affect gase mileage.

Even though I didn't have specific numbers to back it up, it's exactly
for that reason I sometimes alter my route to use smoother roads...
assuming that doesn't entail a significantly longer trip.

If anyone doubts that a rough road can make a big difference, it's
simple physics: it takes energy for a bump, or series of bumps, to shake
your car, and that energy is coming from what would otherwise be forward
motion (or regen).  

Posted by Bob & Holly Wilson on July 6, 2008, 10:17 pm

When I was researching tire rolling resistance I came across a lot of
information about rolling resistance and the type of road surface. But
since I don't have a lot of control over the road surface, I noted it
but didn't really take any notes.

What tire pressure do you run? How close is it to the maximum cold
pressure for your tires?

Bob Wilson

Posted by king on July 7, 2008, 7:27 pm

Tirepressures is something I have not checked yet. Since the car is on the
road for just 4 days now.
I assume it has the standard pressure. I need to check the big book that
came with the car.


Posted by Tomes on July 8, 2008, 2:35 am
 "king" ...

King, this is one area that the book is not so good on.  Most of us are
using tires inflated rather hard.  I use 42 psi in the front and 40 in the
rear and it adds significant MPG.  Reported wear of tires the I have seen
(in NGs and in real life) is unchanged/not noticed.

Here is another book on-line that is pretty good and is written by users,
not Toyota:
Page 22 discusses tire pressure.
Read this whole thing to learn a lot about your car.  Read the regular
manual as well - there is really good stuff in both.

Hope this helps,

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