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2010 Prius III fuel efficiency hypermiling results

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Posted by Neo on August 21, 2010, 3:51 pm

I purchased a 2010 Prius III in April 2010.  I've been trying out a
variety of hypermiling techniques on it since then and I have
purchased a Scan gauge II recently to refine those techniques.

On short 15 mile summer runs the MFD  says that the Prius has gotten
about 81 mpg; however, the MFD FE computations tends to over estimated
the mpg by 3 to 5 mpg so the FE is probably closer to 75 mpg.
The overall mileage between tank fill ups (usually about 9 gallons or
every 500 miles or so) is much less.
On these extended distances, the 2010 Prius computed mpg has been as
low as 52 mpg  and has high as 64 mpg with the average overall mpg to
be around 60 mpg.

Posted by Neo on August 28, 2010, 5:19 pm

After 578 miles, on my last fillup I computed that the
2010 Prius was getting  61.8 mpg (the MFD estimate was 65.5 mpg).

I finally got to checking the tire pressure
and the tire pressure was too low.
All four tires were at 30psi, Toyota specs the
front tires at 35psi and the rear tires at 33psi.
The OEM Yokohama tires are rated for a maximum
of 40psi. Many on PriusChat  were saying they
had set the front tires at 40psi and the rear
tires at 38 psi. The 5psi over the the official
recommend psi level is suppose to increase
FE without causing problems in handling and
tire wear. I am a bit worried of setting the front
tires at their max psi ratting so  I set all four
tires at 38psi.

I just installed a Scan Gauge II on the 2010 Prius. The
most useful gauge is the instantaneous MPG and the
RPM. The Instantaneous MPG shows a finer level of
detail than the Prius's MPG bar chart.  It is useful to
monitor the RPM to see how hard the ICE is working.
The AVG (average mpg) seems to output the same
number as the Prius average MPG display.

With the scan gauge II and the higher
tire pressure, I hope to improve my FE
score will improve.

Posted by Neo on September 25, 2010, 12:01 am
I've raised the tire pressures to 40psi front and
38 psi rear. Even with the scanguage II - it is still
difficult to get the car's computer FE display to
register higher than 67 mpg over 200 miles.
(my actual top mpg during the summer is
probably slightly under 64 mpg). I suspect that
with better LLR tires, Michelin E/S,  the mpg
could be improved by 2 or 3 mpg.

Getting FE higher than 67 mpg appears to
depends on finding a better route and given
the traffic pattern. To optimize hypermiling
a commuting route need to have atleast two lanes in
one direction(so other car can past you),
have very few stop signs and traffic lights
(so you could maintain the vehicle's momentum
as long as possible),  be relatively flat
over a long distance(so energy would not
have  to be expended going uphill in
either direction) , have a smooth road
surface (to extend the coasting time of
the car), and allow the car to go between
35 mph to 45 mph without impeding
the general traffic flow( which is the optimum
speed for the maximum fuel efficiency of
the vehicle)..

Posted by Neo on November 10, 2010, 1:22 pm
Colder temperature and the switch over to the winter fuel
blend of gasoline has cause the fuel mileage on the last tank
of gas ( +9 gallons, 540 miles, 58 mpg ) tp drop about 2 mpg.
The sudden drop in temperature and bad weather has made
it more problematic to maintain the tire pressure at
42 psi front and 40 psi rear.  A drop in just one or two psi
will lower the coasting ability of the Prius and cause the
MPG to drop - so I've increased the tire pressure to 44 psi
front and 42 psi rear.  The drop from 70F-50F to 40F-30F
temperature range forces the ICE to burn gas to warm up
the engine/catelytic converter (or recharge the battery) more
often -- after a full warmup cycle the overall mileage(AVG)
on the Scangauge II drops by about 3 to 5 mpg.

I tested a sub-route with no stop signs or lights but
with many steep short hills verses my usually sub-route
with a few stop lights and only a few less steep long hills.
( Georgia/Norbeck vs Georgia/Muncaster/Redland)
When subtracting traffic factor (by driving when
nobody is using the road)  it is easier to hypermile/coast
on roads that have fewer longer flatter grade hills
than if the roads have many shorter steeper grade
hills - if there are only a few stop lights that are
easily seen from a distance the  driver can
alter the car's speed to "time" the car so it does
not have to stop at the light (thus conserving the
car's momentum) so thus there does not have to be
a penalty for having traffic lights. However the penalty
for multiple steep hills is fixed. The penalty for using a
route with many more steeper hills was about a lost of
5 mpg. Essentially the shorter and steeper the
road grade is the more difficult it is to get the
downhill MPG gain to overcome the uphill MPG
loss. When driving through multiple short steep
hills without stopping  one must maximize the MPG
at each downhill grade to mitigate MPG losses from
going up each uphill grade. A short burst of power
at the very top of the hill is more useful  in gaining
speed and momentum ( to go help going up the
next hill) than applying the power at the bottom
of the hill. To get the best MPG,  the uphill speed
must be allowed to drop as the car goes up the
peak of the hill - attempting to accelerate or
maintaining the cars speed uphill will case the
MPG to drop.  How far one can allows the MPG
is heavily dependent on traffic conditions.
Because the Prius is very heavy and its
power to weight ratio is not all that high -
FE suffers more during low speed acceleration
and uphill  climbing than if it were lighter
car or a car with a more powerful ICE/MG.

As the winter approaches - I am investigating
blocking the front air intakes to help the ICE stay warm.
This requires monitoring the coolant temperature (FWT)
so that the engine does not over heat.

2010 Prius III, Yokohama Avid S33 (44psi front, 42psi rear),
Scangauge II ( RPM, MPG, FWT, AVG)
current MPG (fcd) = 60 mpg
Overall estimated MPG = 60 mpg, 5700 miles

Posted by Bruce Richmond on November 12, 2010, 6:13 am
Blocking off the lower openings on my 2001 Prius allowed it to warm up
in about half the time, increasing my avg mpg by about 4 mpg doing
mostly 11 mile trips.

Tire pressure can also make a big difference.  Going from 35 to 45
gained about 5 mpg.  Cold temps will lower the pressure.  Keep
checking as it gets colder.  I am currently running 50 psi all
around.  Good for maybe 2 mpg better than 45 psi.

Went from running 5w-30 Mobil 1 oil to 0w-30.  Will be trying 0w-20 at
next change in about a month.  Should help mpg with the cold weather.
Car starts fine in the cold (sub zero F)even with 5w-30.

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