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.
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.
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 Scangauge II on my Prius has indicated
that I was able to achieve over 55 miles per gallon
by using Plus and Glide(P&G) cycle on a smooth road
with slightly hilly terrain. This technique involves briefly
accelerating (> 2000 rpm ) to achieve 45 mph and then
pulling back on the accelerattor so that the HSI is
in the middle of the ECO bar ( about 1200 RPM) and
allowing the speed of the Prius to decrease to around 33
mph before attempting to repeat the .P&G cycle all over again.
This technique feels strange at first since the results
are better than if one attempts to maintain
a constant lower speed (35 mph) and allow
the car to decrease its speed slightly(26 mpg) over
the same route. While the ICE burns
more gas during acceleration if the time of
the acceleration burst is kept very short it
could burn less gas than if the ICE is kept
running at a lower but uniform burn rate
over the same amount of time. The Prius
because it is very heavy maintains its speed
due to the kinetic/stored potential energy created
during the acceleration. The trick is to avoid reaching
a top speed that is faster than necessary. The top
speed should not be any faster that the speed
it would take so that if the Prius had to come
to a full stop that by letting go of the accelerator
one would have enough distance in front of the
Prius so it could to coast to a stop. This is
not practical in urban driving so a compromise
top speed needs to be selected for a given section
of a well know route. Knowing a good top speed
for a section of road is key to obtaining the best
FE results from a P&G cycle. Once the top desired speed has
been achived- the driver drops the speed of Prius ICE
to its most efficient mode which is indicated by being
at the center or slightly right of the center of the ECO
bar in the HSI indicator display OR the driver run the
Prius only on the electric motors by pressing the accelerator so
that HSI indicator bar is on the left side of the ECO.
2010 Prius III, Yokohama Avid S33 (40psi front, 38psi rear), Scangauge
current MPG (fcd) = 65 mpg
Overall computer MPG = 60 mpg, 5400 miles
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
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.
In the last four weeks the average temperature has dropped
about 20 degrees Fahrenheit and the fuel efficiency of my
2010 Toyota Prius III has dropped from 62 mpg to 58 mpg.
When the temperature drops from 60 F to 40 F the mpg
drops about 10 mpg using the same route w/ hypermiling
techniques in approximately the same driving conditions
- the reason it seems is that in stop and go slow urban
driving conditions the 1010 Prius ICE must run more often
to warmup the coolant/emission devices. To try to boost
FE - I am implementing the last hypermiling trick I know
- grill blocking. I am blocking the the lower grill by 100%
and I will monitor the coolant temperature via the Scangauge
II. The objective is to make sure the ICE stays warmer and
thus has to run less frequently to keep the coolant
and emission device warm.
While some tires have a max psi rating of 50 psi,
the Yokohama Avid S33 has a maximum tire
pressure of only 44 psi so I've avoided increasing the
tire pressure any further than 44 psi (at least for now)..
2010 Prius III, Blue Ribbon/Dark Grey
Yokohama Avid S33 (44psi front, 42psi rear) <== hypermiler mod #1,
Scangauge II ( RPM, MPG, FWT, AVG) <== hypermiler mod#2
lower grill blocked 100% <== hypermiler mod#3
upper grill unblocked
DC/MD/VA metro area
worst MPG (550 miles) = 54. mpg
best MPG (300 miles,) =66 mpg
current MPG (fcd) = 58 mpg
Overall estimated MPG = 59 mpg, 6300 miles
The temperature in the Washington DC Area has dropped
down to a high of 40 F degrees to a low of 28 F degrees.
Fuel efficiency on my 2010 Toyota Prius III droped down
to an average of 55 mpg for a oneway 12 mile commute
- this is down from an average of 65 mpg for the same
12 mile commute during the summer time. The problem
is not with the tire's rolling resistance (tire pressures is
44 psi in front and 42 psi in the rear) but with the lower
power performance from both the ICE and MG during
the colder temperatures. Also using the defroster/heater
during the winter lowers the ICE energy efficiency.
Furthermore, It takes more energy for the ICE to keep the
emissions control equipment at the proper temperature
when the outside temperature is near freezing.
To help keep the ICE warm - I've started to block
both the top and bottom grills - during the 12 mile
commute. I am monitoring the coolant temperatures
via ScangaugeII via the FWT gauge. The ICE
water/coolant temperature is peakomg somewhere
between 160 F to 188 F degrees ( If the ScangaugeII
FWT climbs to 200 F degrees I plan start removing the
top grill blocking ) so far there has been no hint
that the ICE might overheat due to the grill blocking.
I've notice that grill blocking has reduce the number
of time the ICE needs to run inorder to keep the
ICE/emission temperature up...
2010 Prius III, Blue Ribbon/Dark Grey,OEM floormats
Yokohama Avid S33 (44psi front, 42psi rear) <== hypermiler mod #1,
Scangauge II ( RPM, MPG, FWT, AVG) <== hypermiler mod#2
lower grill blocked 100%, upper grill blocked 100% <== hypermiler
DC/MD/VA metro area
worst MPG (550 miles) = 54. mpg
best MPG (300 miles,) f mpg
current MPG (fmd) = 57 mpg (dropping)
Overall estimated MPG = 59 mpg (dropping), +6500 miles
Temps here in New Hampshire have been in the teens lately and are
dropping. With lower grill blocked I am still getting about 6 mpg
less than in the summer. Will be getting a scangage II soon so that I
can tape over the upper grill as well.
On the pulse and glide technique, I'd just like to add a bit to what
you wrote back in Sept. The idea is to put the engine under more load
part of the time to reduce the losses due to drawing a vacume against
the throttle plates, and then to shut the engine off. This is an old
trick used in economy runs with normal non-hybrid cars. The car, with
a manual transmission, would be accelerated at full throttle in high
gear to a fairly low speed to avoid wind drag. It engine would then
be shut off and the trans slipped into neutral to coast.
For the Prius you want to keep the speed down low enough so that when
you let off the gas the engine shuts off and stops turning. For my
2001 that speed is 41 mph. Above that speed the engine keeps turning
to keep from over speeding the motor/generator. When you let off the
gas and the engine shuts down the electric motor starts regenerative
braking. There are losses when charging and discharging a battery, so
to avoid those losses you gently press on the gas. You don't want to
step on it so hard as to use the electric motor to propel the car,
because that would drain the battery which would then need to be
recharged. The trick is to work the gas so that the car is just
coasting, as if it were in neutral. That is the glide, without
power. You are basicly doing the same thing as the old car above, but
are able to control everything with just your foot on the gas.
The roads around here are mostly 2 lane, and coasting down to 20 mph
in a 35 zone with traffic behind you isn't really an option. Under
such circumstances I have found that a modified pulse and glide still
gives better mileage than a steady light throttle. Let off the gas to
shut the engine down, then step on it lightly to use the electric
motor to maintain your speed. When the battery gets drained enough,
or the engine cools, it will start up again. It will have to work
harder to recharge the battery while propelling the car, but the fuel
saved while it was off more than makes up for that used to charge the
This is essentially the technique I use with my 2010. Since my
commute to work ends with a roughly 7/8 mile low-load (all either
downhill or level, low speed) run, and my commute home ends with a 2.5
mile or so low load run, I'm able to drive those last sections with the
ICE running but the electric motor doing all the driving. This raises my
average about 1.1 MPG going to work, and 2.5 coming home. Since the ICE
is going to have to run a lot to warm up the next time the car is
started, it may as well be charging the battery pack as well. The
battery pack is never below two bars when I shut the car off, and is
usually at 4 or 4.
Hypermiling in cold weather
The local ambient driving temperature has dropped to a range
somewhere beteen 37 Fahrenheit to 27 Fahrenheit with the
average about 32 Fahrenheit. I've increased the tire pressure
to about 48 psi front and 45 psi rear on the Yokohama Avid
S33. The ride is very taut but the Prius tends to coastdown
hill much easier at this tire pressure setting. Blocking the
top and bottom grills on the Prius has lessen the need for the
ICE to turn on to heat the emission catalytic converter and has
help keep the fuel efficiency up. Even with 100% blocking
on the top and bottom, it takes about 45 minutes for the coolant
temperature ( as read by the ScangaugeII FWT gauge)
to get to the normal operating temperature of 157-188 Fahrenheit.
( For the first five minutes of driving in this kind of cold
weather, the Prius fuel efficiency is between 20 mpg to
30 mpg, After 30 minutes of driving in this kind of cold
weather, the Prius fuel efficiency increases to about 35 mpg
to 45 mpg. After 45 minutes of driving in this kind of cold
weather, the Prius fuel efficency increases to about 45 mpg
to 55 mpg. After 60 minutes of driving in this kind of cold
weather, the Prius fuel efficiency seems to level off
somewhere from about 48 mpg to 60 mpg) - Short trips
in cold weather can really hurt a Prius' Fuel Efficiency.
Over the last two months that I have been grill blocking,
the coolant temperature has only briefly touched 192
Fahrenheit, the ICE has been operating well within its coolant
operating temperatures ( Note that I have not driven the
car for over 90 minutes during the last two months)
For the last four weeks, the Prius mileage has dropped to
52 miles per gallon - a new low. The off brand
anti-fogger that I applied on the interior of the windshield
has lessen the times I've needed to use the defroster
(which has help keep the Prius fuel efficiency higher)
but at this temperature I still have to use it occasionally
- I am wondering whether I applied enough or whether
I should have stuck with a brand name anti-fog application.
Because using the heater would lessen the Prius's fuel
efficiency, I am not using cabin heat - which makes driving
in this weather - a very cold situation. I am thinking that
maybe I should get a better driving overcoat (9_9) .
It looks like that as long as the *winter formula* gasoline is
being sold -- the Prius MPG is going to be significantly
2010 Toyota Prius III, Blue Ribbon/Dark Grey, OEM floormats
Yokohama Avid S22 (front 48 psi, rear 45 psi)
ScangaugeII ( RPM, MPG/AVG, FWT, GPH)
lower grill 100% blocked, upper grill 100% blocked
DC/MD/VA metro area
odeometer = +7000 miles
best FE= 66 MPG (approx 300 miles)
worst FE = 52 MPG ( approx 400 miles)
When he runs into me on the road, I'm going to take his tire pressures
and add them to the police report. When the insurance companies start
bickering, I'm going to make sure his insurance company knows that he
was misusing the car in a dangerous way.
Not covered by insurance, trust me.
Raising the tire pressure has not made the car more dangerous, trust
My test indicate that these the tires appear to be designed to handle
additional pressure and that handling and braking are the same. I
because I had the tires set at recommended 35/33 psi setting initially
and I can tell you that the braking and the handling are about the
for normal urban-highway driving conditions. I've read that the
Avid S33 can be set to 50 psi in the front and 48 psi in the rear -
However, I have not tested this setting yet. There is about 8 mpg to
FE performance improvements going from a 35 psi front and 33 psi
rear to a 44 psi front and 42 psi rear tire pressure setting when
hypermiling. However, there does not appear appear to be any
significant improvement by going over that setting to 48 psi
front and 46 psi rear.
So far, I haven't seen any reports indicating insurance companies
any opinion on hypermiling - positive or negative. However, I don't
the police would easily allow you to add something to a police
report because that would imperil their objectivity as a neutral
party in the eyes of the court. I am not aware of any judicial
about under what conditions overinflation of tires can constitutes
a misuse or dangerous use of a vehicle. However, if you have any
court papers to indicate this to the contrary I am very interested.
So far - I've seen very little substantial and rational evidence on
topic of tire overinflation. I've been experimenting with hypermiling
in part because - there is no way to find out what I need to know
experimentation. - if you could provide such information -
it would save me alot of time.
Most of hypermiling occurs as speeds lower than 40 mph, with slow
accelerations, slowly coming to a stop, yielding to faster vehicles
and yielding to pedestrian along the way - its highly unlikely that
during this hypermiling experiment I will hit anyone. Hypermiling
is a very passive form of driving and tends to extend the time it
takes to get anywhere. There are alot of crazy drivers out there
but I am driving so slowly that they can easily drive rings around
me or I can get out of their way in time.
Absolutely it changes the handling, away from what the entire suspension
was designed to be.
The tires ARE an integral part of the suspension, and in fact those
little tire patches are the only thing touching the road.
Change that, and you change the dynamics of the entire car.
It doesn't matter if the TIRES are designed to handle the pressure. Why
would you even incorporate that into your thinking about the dynamics of
Do you believe that all that matters is "can the tires take this"?
And you have zero idea if "braking and handling are the same". All you
know is YOU haven't found the edge of the envelope YET.
But you aren't testing it for hundreds of thousands of miles under all
types of conditions--that is, until you meet one of those conditions
that the car SHOULD be able to handle with an average driver.
When it doesn't handle it the way it was designed to, YOU are the sole
factor at fault. Not Toyota.
When you hit me, I will take your tire pressures and add them to the
Yokohama Avid S33 Tires at these higher
air pressures do not appear to have any additional
tendency to hydroplane. However, the higher
air pressure means that the tires transmits
more shock from road irregularities than if
the tires were set at alower air pressure. I've
only recently upped the tire pressure but I have
not notice any problems with traction or handling;
however, since I am driving this Prius for fuel
fuel efficiency - I am not testing the upper limits
tire's handling characteristics or its braking
performance as might another. Sofar the tire
treads doesnot appear to be wearing out prematurely
or wearing out in an irregular manner -- however
I will keep an eye on this possible complication.
Reviews suggest that this particular tire has a
lifespan of about 20,000 miles - so I am expecting
to replace them in the next two years with something
better. I've read some negative consumer reviews
that complain that the Yokohama Avid S33 Tire
have poor snow and ice handling. Earlier this
year the Washington DC area was hit by a
big snow storm - but unlike certain northern
areas of the USA snow storms are a rarity
for this area - so I am unlikely to have a chance to
test this tire's actual snow and ice handling
characteristics before the tire tread wears out
The Yokohama Avid S33 Tires are designed for
only light snow - they have only fair snow and
ice traction performance. Because, snow
and ice are a rarity in my area - it may not be
an issue for me since reviews of this tire suggest
that they are not likely to last more than another
18 months. When I get replacement tires I am
thinking of getting Hankook Optimo H727,
Consumer Reports ( July 2010, page 50-51)
reports they have very good snow and ice handling
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