Toyota Prius HSD User Manual
Toyota Prius User-Guide
Fifth Edition, First Revision for the HSD (2004-2006) model
DRIVING ..........................................2
Just Drive It !..............................2
Startup........................................2
Shutdown ...................................3
Cruise-Control............................3
Neutral .......................................3
Reverse.......................................4
Hybrid Driving...........................5
Brakes ........................................5
Stealth Driving ...........................6
"B" Mode ...................................6
Radio..........................................7
CD..............................................7
Audio Buttons ............................7
Inside Air ...................................7
Outside Air................................. 8
UNDERSTANDING......................... 9
MPG Measurement ....................9
Increasing MPG .........................9
EPA Estimates..........................12
Seasonal Cycles .......................14
Emissions.................................15
NURTURING ................................. 16
Filling the Gas Tank.................16
Multi-Display Care ..................17
Long-Term Storage..................17
Polishing ..................................18
Tire Care ..................................18
Upgrade Tires ..........................20
Washing ................................... 22
Valet Use .................................22
MAINTENANCE ........................... 23
Oil Changes..............................23
Window Wipers ....................... 25
Air-Conditioning...................... 27
OPTIONS........................................ 28
(SE) Smart-Entry .....................28
(SS) Smart-Start .......................28
Homelink .................................29
Bluetooth..................................29
Navigation ............................... 30
Voice-Recognition................... 30
Electrochromic Mirror ............. 30
VOICE-RECOGNITION .............. 31
Help .........................................31
Navigation - Commands .......... 31
Navigation - Locations............. 32
Audio ....................................... 33
Climate .................................... 33
Screen ...................................... 33
OTHER...........................................34
Battery-Pack ............................34
Rear Hatch ............................... 34
Side Mirrors.............................36
Transmission............................ 37
Information Sources................. 37
Informational Materials ...........38
GLOSSARY ................................... 42
Disclaimer:
All the information stated in this document was provided by Prius owners. None were affiliated with Toyota Motor Corporation,
except as customers.
This document is not sanctioned by Toyota Motor Corporation or any of its affiliates.
The ideas, suggestions, and opinions offered in this document have not been endorsed by the manufacturer of those specific
components or Toyota Motor Corporation.
Any harm or damage that may result from the application of or the following of any ideas, suggestions, or opinions contained in
this document is the sole responsibility of the individual that applied or followed said ideas, suggestions or opinions.
The authors of this document hereby declare that they cannot and will not be held liable, in any fashion, for the content or the use
of this document.
DRIVING
Just Drive It !
Vital Info
Startup
Step On the Brake
12-Volt Jumping
Winter Heat
Ignore all the advanced technology!
It's too easy to get preoccupied with everything Prius automatically does for you, especially with
the Multi-Display providing constant performance information. The hybrid system was designed
so you could to drive it like a traditional car. That way, you can enjoy the remarkably smooth &
quiet ride. Let the computer worry about how to save gas and reduce emissions.
New owners sometimes fall victim to this, not being able to figure out why the car won’t start.
For safety, stepping on the brake before starting has always been highly recommended in all types
of vehicles anyway. But in Prius, it is required. Because if you don’t, you’ll find that only the
accessories will power-up. The hybrid system itself won’t start until you push the power button
while also stepping on the brake at the same time.
If you do make the mistake of not pressing the brake pedal far enough to the floor, a collection of
warning the lights by the speedometer will come on. In that case, lift your foot off the brake. Wait
a few seconds, and then press it again... only harder this time. Wait a few more seconds, and then
press the PARK button. That will reset the system.
If the 12-volt auxiliary battery is ever drained completely, you can jump it similar to a traditional
vehicle. With the Prius OFF (hybrid system & lights), connect the positive-cable to the jump-start
terminal (within the black plastic fuse-box, under the Prius hood) then to the positive-terminal on
the 12-volt battery of the supplying vehicle (as it is running). Next, connect the negative-cable to
the negative-terminal on the 12-volt battery of the supplying vehicle. Then the other end of the
negative-cable can be connected to an unpainted metal component under the hood; a very good
place for this is the support attaching the engine & motor to the body of the vehicle in the front
driver's side corner under the Prius hood. At this point, start the hybrid system. When "READY"
appears on the Prius speedometer cluster, you should then disconnect the cables following the
opposite order they were connected.
For safety information, greater detail, and illustrations, please refer to your Owner's Manual.
A very simple way to confirm you have a good electrical connection before attempting to start is to
just turn on the ceiling light. If it illuminates brightly, you know that the supply coming from the
donor vehicle is sufficient to successfully jump the Prius. If the light is dim, the connection is bad
and you must fix it before proceeding.
Creating heat for the emissions system and heat to keep you warm is fastest and most efficient if
you simply drive gently immediately after starting the Prius in the winter. Allowing the engine to
run while the Prius is parked takes longer and is less efficient. "Just Drive It
Once the heater warms up, resist the temptation to turn up the fan-speed on too high. That will
actually decrease the potential heat. Air blasting over the fins of the core too quickly prevents the
opportunity to absorb as much heat as possible. Slower air doesn’t. In other words, don't exceed
the medium speed setting.
!"
Prius User-Guide 2 of 45 Last Updated: 2/07/2006
Engine Warm-Up
Reducing Emissions is the highest priority for Prius. It strives to remain a AT-PZEV (Advanced
Technology - Partial Zero Emission Vehicle) at all times, which means the catalytic-converter must
be kept warm even if it requires consuming some gas to accomplish that. Fortunately, you still get
better than average mileage, even if the engine doesn't shut off right away.
Shutdown
Off Confirm
Whirring Sound
Use the remote or push a door-button (or the one on the hatch) when leaving your Prius. That will
confirm that all the doors really did get shut tightly and the power for the hybrid system is off. If
you don't, the 12-volt auxiliary battery may get drained completely or the alarm might not be able
to protect the car.
There is a small electric-pump that pumps 3 liters of coolant into a thermal container (to keep it hot)
every time you turn the hybrid system power OFF. When the power is turned back ON, the coolant
is pump back into the engine. This process reduces emissions, by achieving warm-up much faster
than with an engine that would normally have to heat itself up. This process also helps to reduce
wear & tear on the engine.
Cruise-Control
24 MPH minimum
MPG
Stealth
Smooooooth
Neutral
No Engine
Slowing down to less than 24 MPH (39 km/h) will cause the cruise-control "resume" memory to
reset. So if you have to slow down or stop, you'll need to set the speed again.
Some owners have observed an increase in MPG from using the cruise-control, others have not.
Results vary depending on your particular driving habits and road conditions.
If you don't have a sensitive enough foot but would still like to enjoy stealth driving on a light
traffic road, just set the cruise-control. This can be done all the way up to 42 MPH (68 km/h) on
flat or declining terrain without making the engine startup.
The CVT (Continuously Variable Transmission, "Planetary" type) makes the cruise-control in Prius
remarkably smooth. You'll notice the "no shifting" characteristic of the drive when going up hills
and accelerating aggressively. Many consider this smoothness as a luxury feature.
To shift into neutral and keep it there without any chance of the engine starting, do the following:
1. Insert the FOB (not necessary if you have SE/SS).
2. Without stepping on the brake pedal, press the "Power" button twice.
3. Use the lever to shift in the Neutral position.
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Reverse
Beeper Disable
Some people find the reverse beeper distracting. Although there isn't a method to change the
repetitive beeping to just a short warning, there is a way to disable it completely. To do that,
carefully follow these steps:
Switch to the odometer/trip value to display "ODO" by pushing the “ODO TRIP” button
1.
shown in the lower-right corner of the photo below. If the speedometer-cluster was
already showing “ODO”, make sure to cycle thru each option back to “ODO” again.
Power OFF (push the "Power" button).
2.
Power ON (push the "Power" button again).
3.
Within 6 seconds of powering back ON, push & hold the button for “ODO” for a
4.
minimum of 10 seconds.
While still holding the button for "ODO", shift into "R" (Reverse), then to "P" (Park).
5.
"b-on" should display on the odometer/trip-meter now. Push the "ODO TRIP" button
6.
to switch the mode to "b-oFF", as shown here:
Power OFF (push the "Power" button). That’s it! The beep should now be disabled.
7.
If the sequence above failed, it may have due to the "ODO" setting not having been visible
Note #1:
recently. In that case, all you have to do is drive with it that way for a few miles. The next
time you try to disable the beeper, the process should work.
Note #2: If you ever disconnect the 12-volt auxiliary battery from the system (or drain it dead),
you may have to repeat the disable process again.
Prius User-Guide 4 of 45 Last Updated: 2/07/2006
Hybrid Driving
From a Stop
Climbing Hills
On the Highway
Without the Pack
A/C Instead
Cruising
The gasoline engine is most efficient when running around 70% maximum. So if you can't press
lightly enough on the pedal to accelerate using only electricity, go ahead and press a little harder
than usual. That brisk (but not aggressive) increase in speed will save a small amount of gas,
resulting in an overall efficiency gain.
The hybrid system has 2 electric motors. When you encounter a large hill, those motors are
automatically taken advantage of. The gasoline engine will rev to its most efficient high-power
RPM. That provides thrust directly to the tires, generates electricity for the motor, and recharges
the battery-pack all at the same time. So to the surprise of many new owners, large hills don’t drain
the system. You’ll still have plenty of reserve power available when you reach the top.
Just like with traditional vehicles, efficiency drops the faster you drive on the highway. 60 MPH
(96 km/h) is more efficient than 70 MPH (113 km/h). Speeding up to 75 MPH (121 km/h), you'll
observe MPG drop even more. It pays to drive slower.
The electric motor doesn't actually need electricity from the battery-pack. The gasoline engine
creates electricity immediately while you drive. So quite frequently, on the multi-display you'll see
that the motor is being fed directly from the engine and the battery-pack isn't even being used. And
sometimes, while both the engine and motor are providing thrust, the engine will also recharge the
battery-pack at the same time.
At highway speeds, using the A/C (air-conditioner, cold setting) or vent to remain cool will likely
result in slightly higher MPG than having the windows open.
A beneficial technique for efficient cruising is to feather the accelerator pedal at particular times.
Learning to do this is simple and will quickly become second nature with very little practice. (In
fact, you may already have that foot control if you in-line skate or bicycle occasionally.) To do it,
just lightly reduce pressure on the accelerator-pedal whenever you encounter a section of road
that’s perfectly flat or has a slight decline. The MPG indicator will sometimes jump all the way to
the +100 mark, even though your speed ends up dropping only 1 MPH. Then lightly push the
accelerator-pedal to efficiently regain that speed afterward. Overall, MPG will climb a little bit
when each time you do that.
You’ll end up taking advantage of the hybrid design. Changes in the road pitch naturally cause
changes in speed anyway. Using the multi-display and large digital speedometer helps you
discover when gains from that are possible.
Brakes
Regenerator
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When you reduce pressure on the accelerator-pedal or use the brake-pedal, excess speed turns a
motor, causing regeneration of electricity to recharge the battery-pack. The regenerator takes
advantage of the kinetic energy that would have otherwise been lost. The brake pads & shoes are
not used as much as in a traditional vehicle. This not only makes the Prius more efficient, it also
indicates the brakes will last longer.
Stealth Driving
Engine Off
Up to 42 MPH
Acceleration
A/C & Heater
Be Careful !
While the gasoline engine is off and you’re driving using just battery power, the mode you’re in is
called "stealth" (since movement is totally silent).
Invoking "stealth" is easy once the engine has warmed up (and you aren't running the A/C or Heater
too heavily). While driving, just find a street section without any inclines then lift your foot from
the accelerator-pedal. The engine will shut off within a few moments. Once it does, lightly place
your foot back on the accelerator-pedal to continue driving with only electricity. Another way to
invoke stealth is to just stop completely, that will make the engine shut off.
The 50 kW electric motor is designed to propel the Prius up to 42 MPH (68 km/h). It takes a steady
foot though. Slower speeds, like 35 MPH (56 km/h) and 30 MPH (48 km/h), are easier. Beyond
that maximum speed or in conditions when additional power is needed, the motor works in
combination with the gasoline engine. Though, you will discover above 42 MPH (68 km/h) that
there are times when the engine will spin (pistons in motion) without any fuel being consumed; it is
a normal function of the Planetary-CVT.
Accelerating in "stealth" can be very slow. Also using the gasoline engine is both quicker and
(surprisingly) more efficient, so don't be afraid to consume a little bit of gas. Remember that even
if you use the battery and get "+100 MPG", the engine must run later to recharge it. So short-term
gains may actually result in an overall loss.
Only the lowest setting for the air-conditioner & heater work in "stealth". Higher settings and
airflow durations longer than a minute or two will require the gasoline engine to run.
Be careful while driving in "stealth", especially in parking lots. Some people use only their ears to
verify that it's safe, not their eyes! So having a car that's completely silent means you'll probably
have someone step out in front of it without even realizing you’re driving right at him or her.
"B" Mode
On/Off Anytime
Engine-Braking
Winter Slowing
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You can engage or disengage engine-braking at anytime while driving.
Avoid using this mode unless absolutely necessary, since it will cause MPG to drop. There is no
charging benefit over regular braking either.
The "B" mode works like an exhaust brake on a large truck (except, it's totally silent). The engine
is used to slow down the vehicle, allowing you to reduce reliance on the regular brakes. So for
steep declines, like driving down a mountain, it's a great way to avoid overheating caused by
friction from the brake drums & shoes.
A special use of "B" is the ability to shift into it on-the-fly without having to take your eyes off the
road. Finding yourself taking a turn on snow or ice a little bit too fast, you'll discover "B" does an
absolutely fantastic job of slowing the car enough to retain traction without any risk whatsoever of
the wheels slipping from braking too hard... since you aren't using the brakes at all.
Radio
Channel Scan
Tuner Adjust
CD
CD Change
Press the "SCAN" button by the radio tuner knob. It will begin scanning for radio channels. When
it does finds a station, a few seconds will play, then it will automatically scan for the next. Press
the "SCAN" button again when you want the scanning to stop.
If you press then hold the "SCAN" button, only your preset radio channels will be scanned.
In additions to using the knob on the dashboard, you also have the option of adjusting the tuner for
the radio via the buttons on the steering-wheel. Just press & hold either the up or down button with
your left thumb.
Holding the track-change button on the steering-wheel, rather than just quickly pressing it, will
cause the CD to be changed instead.
Audio Buttons
Audio Button
Mode Button
Inside Air
Recirculate
Pressing the "Audio" button next to the Multi-Display will reveal the Radio Preset or CD Control
screen, depending on what is playing at that moment.
Pressing the "Audio" button another time will return you to the screen you were previously
viewing, "Consumption" or "Energy Monitor" or "Navigation".
Pressing the "Mode" button on the Steering-Wheel toggles between the AM, FM1, FM2, and CD
modes of the audio system.
Holding the "Mode" button for a few seconds will toggle the power for the audio system on & off.
Avoid using this mode during the winter, since it causes frost on the inside of the windows.
Recirculating warm inside air will prevent the engine from needing to run as often; however, the
moisture you naturally exhale will build up after awhile. Allowing the fresh cold air from outside
to be drawn in will keep the humidity low. The resulting minor MPG penalty is well worth always
having clear glass.
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Outside Air
Vent
Changing the "Air Conditioner" mode to draw in air directly from the outside for cooling rather
than allowing it to be influenced by the heater-core isn’t an obvious process, but it is surprisingly
easily once you know how.
Many people call this "opening the vent" and it is used most frequently in the summer when you
want to avoid having to turn on the A/C.
Here’s how:
1. Press the "A/C" button so the yellow-bar above it disappears.
2. Press the circulation button so the yellow-bar above the "outside car arrow" appears.
3. Reduce the temperature to the lowest setting, called "Max Cold".
The Multi-Display will then resemble the example above.
You may alter the blowing location to any of the 4 settings available and the blowing speed to any
of the 7 settings available.
Prius User-Guide 8 of 45 Last Updated: 2/07/2006
UNDERSTANDING
MPG Measurement
Lifetime
Tank
Trip
Sudden Drop
Tire Break-In
LIFETIME is the most useful measurement. Total miles driven, divided by total gallons consumed,
informs you how efficiently the car has performed overall.
TANK is the measurement between each fill up. You press the RESET button when the tank is
full. The results are informative, but not perfectly accurate. In cold weather, the bladder inside the
gas tank shrinks. This reduces the overall capacity making the "full" level variable. Also, "full"
can be misrepresented if the pump doesn't shut off at the proper time. These factors make
calculations based on fill-up less accurate.
TRIP is mostly for fun, since a multitude of variables can affect the measurement to a single
destination. Watch the 5-minute summary segments shown on the multi-display. Remember
though, if you were to start a drive downhill, with a tail wind, a warm engine, a fully charged
battery-pack, and a warm outside temperature, the MPG would be very impressive for that
particular trip. But then if the return trip back was uphill, against the wind, with a cold engine, a
drained battery-pack, and a cold outside temperature, the MPG would appear very disappointing.
In summary, trip results can vary greatly. The overall average is what really matters.
Tire pressure may have dropped. For every 10 F degrees colder, pressure will automatically drop
1 PSI. Verify you still have as much air in the tires as you think they do.
Increased use of the heater or air-conditioner (which includes the defroster) will force the engine to
run more often. Try a less demanding setting.
When the temperature drops below freezing, you may notice the engine has to run quite a bit longer
to warm up the catalytic-converter. This is to keep the Prius emissions Super-Ultra low. Avoid
driving short trips; instead, take advantage of the time after warm up is complete by running several
errands at once.
A dirty engine air-filter will also cause the MPG to drop. Check it routinely, especially as the
seasons change. Once flow becomes visibly restricted (dark colored rather than white), the time
has come replace it.
Don’t forget that new tires require a break-in period. Before that the tire surface and tread edges
will be rough, causing MPG to be lower than you expect. It takes about 1,000 miles (1,600 km)
before enough wear (barely visible to a trained eye) occurs to allow less abrasive contact with the
road. And since front tires wear more than those in the rear, expect another break-in period the first
time the rear tires are rotated to the front. Fortunately, that reduced MPG will only last a few
hundred miles.
Increasing MPG
A/C & Heater
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Minimal use is the key. Using the Heater or the A/C (which includes the defroster) on anything but
a low setting may prevent the engine from shutting off. That will reduce MPG. So, try to avoid
high demand use. Fortunately, on the highway using the A/C is still more efficient than opening
the windows.
On the Highway
YMMV
Driving
Tire Care
87 Octane Gas
"B" Mode
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Just like with traditional vehicles, efficiency drops the faster you drive on a highway. 60 MPH
(96 km/h) is more efficient than 70 MPH (113 km/h). Speeding up to 75 MPH (121 km/h), you'll
observe MPG drop even more. It pays to drive slower (obey the speed-limit). Think of it this
way, pedaling a bicycle rapidly takes much more energy than pedaling at a moderate rate.
"Your Mileage May Vary" That simple statement about the EPA ratings shown on the new
vehicle window sticker is often overlooked, yet it makes a significant difference depending on the
type of driving you do. Reading this quote provided by the EPA about Prius reveals why: "Actual
Mileage will vary with options, driving conditions, driving habits and vehicle's condition. Results
reported to EPA indicate that the majority of vehicles with these estimates will achieve between 51
and 69 mpg in the city and between 43 and 59 on the highway."
EPA tests are generalizations (performed under ideal conditions) intended to make vehicle
comparisons easier, not to specify what MPG you will actually get. In fact, they rarely reflect the
MPG in real-world driving experiences.
Brisk Acceleration is an often misunderstood benefit. There's no need to hold back. A gasoline
engine works more efficiently when running at higher RPM, about 70 percent of maximum. Take
advantage of that by getting to cruising speed quickly (but not aggressively, please drive safely).
And remember, while the engine running it is also generating electricity for later use.
Coast whenever you have the opportunity. Using the feather technique helps. By lifting your foot
lightly from the accelerator-pedal, you can invoke an efficient computer-controlled glide without
decelerating much at all (less than 1 MPH). With good road conditions and a bit of practice, you'll
find yourself doing this instinctively.
Look Ahead. If you see a light turning red or a need to slow down in the distance, there's no
reason to continue holding the accelerator-pedal. Remove your foot and allow the generator to
decelerate the Prius. That will increase your MPG, charge the battery-pack, and prolong the life
of your brakes.
42/40 PSI (2.9/2.8 bar) is what many Prius owners strongly recommend. The original tires for the
Classic (2001-2003) Prius support a maximum cold pressure of 50 PSI (3.4 bar), for the HSD
(2004-2005) Prius 44 PSI (3.0 bar). So that pressure increase is well within the design
specifications. Many of the alternate tires available support a maximum cold pressure of 44 PSI
(3.0 bar) too. Whatever you decide, just remember that low pressure results in a MPG drop and the
tires wear out faster. Tires will not bulge like in decades past; manufacturers provide much better
quality now which maintains a flat contact surface all the way up to the maximum pressure.
Every 5,000 (8,000 km) the tires should be rotated, for best lifetime performance. Rotation is
preferred in a roll-back, roll-forward pattern.
Measuring the PSI should be done only when the tires are cold, since driving heats up the air
inside the tires making the results inaccurate... giving you the impression more pressure is higher
than it really is.
Check Often since temperature causing pressure to drop, 1 PSI for every 10F degrees. Air will
naturally leak out from normal use too.
Prius was designed to run with 87 Octane gasoline (85 in high altitudes). Some owners have
experimented with higher octanes, but found there wasn't any MPG improvement. Also, bear in
mind that higher octane gasoline may trigger an emission sensor alert. So just save money and
continue using the less expensive 87 octane gas.
Avoid using this mode unless absolutely necessary; it will cause MPG to drop.
External Loads
Engine Warm-Up
5W-30 Oil
Synthetic Oil
Oil Level
Measurement
Break-In
Hitch Racks & Roof Carriers cause aerodynamic drag. So, expect a MPG drop when you use one.
Short Trips are horribly inefficient for all vehicles. Prius is no exception; however, it’s far more
noticeable since the Multi-Display provides immediate feedback to actually show you the lower
MPG. The efficiency benefits of the system are not utilized until after warm-up is complete... that's
engine, emissions system, and tires. So try to run several errands at once to take advantage of an
already warmed up car.
PZEV (Partial Zero Emission Vehicle) is what Prius strives to remain whenever active, even during
warm-up. That means the catalytic-converter must be kept hot even if that requires using some gas
to do it. Fortunately, you still get better than average mileage, even if the engine doesn't shut off
right away.
5W-30 oil is strongly recommended (real or synthetic).
If a service person puts 10W-30 in by mistake, you may complain since it will negatively impact
your MPG slightly and may affect performance in below freezing temperatures. The text on the
engine oil cap clearly states 5W-30 should be used.
Owners have observed minor MPG improvements by switching to synthetic oil.
Plus, since it protects the engine better than real oil and makes extremely cold startups even easier,
switching from real oil should be a simple choice.
Too much oil can decrease MPG. Verify the level is never above the max mark on the dipstick.
Unfortunately, overfilling is a problem commonly overlooked. Oil change services routinely pump
oil from large barrels, rather than using quart-size bottles. That makes overfilling very easy to do.
Taking a moment afterward to check afterward is truly beneficial.
The multi-display averages optimistically, so it will usually read about 1.4 MPG too high for most
owners. The "bladder effect" (caused by the bladder in the gas tank shrinking due to temperatures
below freezing), which is very noticeable in the Spring & Fall, causes the readout value and manual
calculations to vary greatly for individual measurements. Averaging several fill up amounts
documented at the gas station will provide the actual MPG you've been getting. For an example of
how to do this, refer to this webpage...
http://john1701a.com/prius/prius-data.htm
For the first 200 Miles (322 km):
• avoid rapid deceleration (hard stops)
• avoid high speeds (more than 70 MPH, 113 km/h)
For the first 600 Miles (966 km):
• avoid rapid acceleration
• avoid racing (high RPM) the engine
After roughly 10,000 Miles (16,100 km):
• enjoy a MPG increase, from the moving parts having loosened
Even at 30,000 Miles (48,300 km):
• you may continue observe minor MPG increases as the car ages
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EPA Estimates
Purpose
The intent of the EPA efficiency values posted on each new vehicle window-sticker is only to
provide a basis for comparison, not an actual MPG expectation... as commonly believed.
Read the fine-print on this scan of a 2004 Prius window-sticker:
Don’t be mislead by the big numbers. Real-World results vary significantly.
Ideal Conditions
Ranging Values
Unrealistic Speed
Unrealistic Climate
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Pay very close attention to the fact that the EPA tests are all performed under ideal conditions,
those that don't actually reflect real-world temperature or driving habits. Think of those values
reported as optimal, not realistic. You may be able to achieve them from occasionally, but not on
a routine basis.
As mentioned on the window-sticker, there is a range of expected efficiency values. The large
numbers are really nothing but an average. In fact, the MPG isn't even constant for each vehicle.
Driving conditions, method of driving, and the influence of multiple drivers can all have a major
impact, causing fluctuation. Tank-to-tank measurements can vary quite a bit as a result, without
even taking into account the effect of seasonal cycles. None of these factors are represented when
the EPA tests are performed.
Back when the testing procedures were established way back in 1977, the speed limit on most
highways was only 55 MPH (88.5 km/h). That’s quite unrealistic for travel nowadays. Many
drivers cruise at speeds much faster. That causes a significant efficiency reduction, which is not
indicated on the window-sticker.
The "perfect summer day" climate portrayed during the testing is not what people actually drive
their vehicle in a great majority of the year. Winter extremes cause efficiency to drop significantly,
as do the Summer extremes. Factors such as temperature, wind, and moisture have a major
influence, causing the vehicle performance to be reduced in the form of lower MPG. To make
matters worse, the use of the Heater or A/C also contribute to lower MPG.
Gentle Acceleration
Fuel Type
Testing Procedures
The testing procedures utilize gentle acceleration, which does not represent the way people actually
drive anymore. For example, when merging onto a highway now, much more harsh acceleration is
required. The tests don’t reflect the MPG penalty that causes. So unless you acceleration as slowly
as when the test was performed, efficiency will be lower.
EPA testing is done using 100% gasoline, which is the most efficient fuel available for a Prius to
run on. Those owners using the cleaner fuel alternative called "E10", which is a 10% ethanol and
90% gasoline blend, have a clear disadvantage. That blend is approximated 3.4% less efficient. In
simple terms, that means achieving 50 MPG using E10 could actually achieve 51.7 MPG using
100% gasoline instead.
The following (from http://www.fueleconomy.gov/feg/info.shtml ) explains how the EPA tests are
actually performed, notice how results can be quite a bit lower if you live in the north or if you
drive fast:
The fuel economy estimates are based on results of tests required by the U.S.
Environmental Protection Agency (EPA). These tests are used to certify that
vehicles meet the Federal emissions and fuel economy standards. Manufacturers
test pre-production prototypes of the new vehicle models and submit the test results
to EPA. EPA re-tests about 10% of the tested vehicles to confirm manufacturer's
results in EPA's lab. The vehicles are driven by a professional driver under
controlled laboratory conditions, on an instrument similar to a treadmill. These
procedures ensure that each vehicle is tested under identical conditions; therefore,
the results can be compared with confidence.
There are two different fuel economy estimates for each vehicle in the Fuel
Economy Guide, one for city driving and one for highway driving. To generate these
two estimates, separate tests are used to represent typical everyday driving in a city
and in a rural setting. Two kinds of engine starts are used: the cold start, which is
similar to starting a car in the morning after it has been parked all night; and the hot
start, similar to restarting a vehicle after it has been warmed up, driven, and
stopped for a short time.
The test used to determine the city fuel economy estimate simulates an 11-mile,
stop-and-go trip with an average speed of 20 miles per hour (mph). The trip takes
31 minutes and has 23 stops. About 18 percent of the time is spent idling, as in
waiting at traffic lights or in rush hour traffic. The maximum speed is 56 mph. The
engine is initially started after being parked overnight. Vehicles are tested at 68 F to
86 F ambient temperature.
The test to determine the highway fuel economy estimate represents a mixture of
"non-city" driving. Segments corresponding to different kinds of rural roads and
interstate highways are included. The test simulates a 10-mile trip and averages 48
mph. The maximum speed is 60 mph. The test is run with the engine warmed up
and has little idling time and no stops (except at the end of the test).
NOTE: To make the numbers in the Fuel Economy Guide more useful for consumers,
EPA adjusts these laboratory test results to account for the difference between
controlled laboratory conditions and actual driving on the road. The laboratory fuel
economy results are adjusted downward to arrive at the estimates in the Fuel
Economy Guide and on the labels seen on new cars, light trucks, and vans. The city
estimate is lowered by 10% and the highway estimate by 22% from the laboratory test
results. Experience has proven that these adjustments make the mileage estimates in
the Fuel Economy Guide correspond more closely to the actual fuel economy realized
by the average driver.
Prius User-Guide 13 of 45 Last Updated: 2/07/2006
Seasonal Cycles
Vehicle Types
Temperature
Seasonal cycles affect all types of vehicles, not just hybrid. But with Prius, you are much more
aware of the MPG changes due to having a Multi-Display constantly informing you of efficiency
performance. With traditional vehicles, owners typically are not aware how much of an affect
climate has on their vehicle’s performance. They just assume MPG remains relatively constant
throughout the entire year. In reality, that isn’t even remotely correct. Large fluctuations are
perfectly normal.
The difference between the warm & cold months is a significant change in MPG. In the winter…
The engine takes longer to warm-up, and the engine is needed to operate the heater. Both cause
more fuel to be consumed. The density of cold air is thicker, making it hard to push through. This
reduces efficiency. In the summer… Running the A/C to keep you cool requires electricity from
the battery-pack. That electricity is ultimately derived from the engine, which consumes fuel to
accomplish that. So, the more you use the A/C, the lower MPG will be.
These examples of real-world data (from
shows the effect of 4 separate Winters & Summers with a 2001 & 2004 Prius in Minnesota:
http://john1701a.com/prius/prius-data.htm ) clearly the
Traffic
Heater
A/C
It is common for people to forget how much traffic patterns change during the winter. Slippery
roads cause major delays, increasing driving time significantly. So even with the benefit of the
hybrid system, there is still a very real plenty for getting stuck in that traffic heavy traffic.
Heat to keep you warm in the winter comes from the engine. Hot coolant is circulated through the
heater-core as long is possible to continue heating the air. But eventually, it cools. At that point,
the engine must restart to warm the coolant again.
The A/C system in Prius is powered by an electric pump, not a pump powered by a belt connected
to the engine. That means in can run for a modest amount of time exclusively using only the
battery-pack, providing a significant efficiency benefit during the summer.
Prius User-Guide 14 of 45 Last Updated: 2/07/2006
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