Prius Misconceptions

Last Updated: Sun. 9/23/2007


Fortunately, many of the misconceptions from when the hybrid was first introduced (back in 1997) have either subsided or disappeared entirely.  Worries about battery-life and operation in extreme temperatures simply don't get asked about anymore.  Seeing so many Prius now on the road has brought the market beyond those early stages of rollout.  Unfortunately, we do still need a reminder of concerns people did have...



Highway Misconceptions.     back to top

There is quite a bit to tell about hybrid operation on the highway... lots of potential for incorrect understanding ...too much that can be assumed.  So, this document devoted to exclusively to the topic was created:  Highway Misconceptions


Winter Misconceptions.     back to top

The topic of driving a hybrid in the winter is prone to confusion.  It often leads to incorrect conclusions being drawn.  So, this document devoted to exclusively to the topic was created:  Winter Misconceptions


Better MPG means cleaner emissions.     back to top

This is a troubling misconception, a belief leading to misinformed purchases.

Only CO2 (Carbon Dioxide) emissions have a direct relation to efficiency.  Higher efficiency doesn't always mean less contribution toward "Global Warming" (the weather effect that causes storms to be more frequent and more violent, as well as temperatures to fluctuate with greater extreme).  The harmful emissions leading to health problems are not correlated to MPG.

SMOG, which consists of NOx (Nitrogen Oxides) and HC (Hydrocarbons) plus a little bit of CO (Carbon Monoxide), is the type of vehicle emission that is harder to quantify, since MPG makes no difference.  This pollution contributes to that nasty orange haze floating above most all of the major metro areas throughout the United States, which leads to breathing complications for young children and the elderly.

The "SULEV" emission rating was created to identify vehicles that were specially designed to reduce SMOG related emissions.  The classic Prius achieves that criteria.  The newer model Prius actually exceeds it (having earned the "AT-PZEV" rating).  Some traditional vehicles actually are SULEV too, believe it or not; but unfortunately they are only available in California and their MPG is very disappointing (even lower than their polluting counterpart).  Lastly, not to put down the other hybrids, but... not every type offers SULEV cleanness; some are only ULEV, which is 72% dirtier with respect to SMOG related emissions.  So don't just assume the highest efficiency equates to the lowest emissions.


Acceleration is too slow.     back to top

Don't fall for market brainwashing!

The classic Prius proved that 0 to 60 MPH acceleration in 12.5 seconds wasn't actually a problem, despite what those promoting "you need faster" will try to convince you of.  The speed ceiling was exceeded years, faster gains you nothing.  But since the concept of "more is better" for speed is what helps to sell vehicles, the advertisers continue to push that aspect... even though traffic speeds are the same as they were in the past.  It's overkill, not actually needed.  Just ask yourself when was the last time you actually had to push the pedal all the way down to the floor in a fairly new vehicle.  Odds are very high that you haven't.

Despite that reality of extra acceleration power being a waste, Toyota decided to offer more.  After all, it is far less wasteful implementing greater power from an electric-motor than it is from a gas-engine.  And since increasing the size of the motor also meant more electricity could be regenerated every time you step on the brake-pedal, it was an excellent opportunity.  As a result of that decision, Prius is now capable of 0 to 60 in just 10.1 seconds.  Plenty of power, even for the skeptics.


The hybrid system lacks power to accelerate quickly.     back to top

Wrong!  Judgment based on sound & feel is very misleading.

People are instinctively trained to resist stress on the engine, based on sound & feel.  The fact that a "full" hybrid like Prius neither sounds nor feels like a traditional vehicle usually doesn't occur to them.  So they unknowingly fight the system at first, not allowing it the opportunity to create thrust the way it wants to.  That hesitation with the accelerator-pedal causes the vehicle to respond slower.

Instead, let the computer decide how to manage the engine for you.  (Remember, it always protects the engine from strain for you by taking advantage of the very durable nature of electric-motors.)  Just push the accelerator-pedal to the point you desire, ignoring the unique sound & feel at first.  Later, you will be able to judge the reaction to your request, just like you can now with a traditional vehicle.  Remember, different does not mean lacking power.  It is simply unfamiliar.


Restarting the Engine frequently is harmful.     back to top

Not True!  That assumption is based on traditional concepts.

Prius starts the engine in a very different manner than methods of the past.

Rather than just using a small motor to spin the gas engine to only 100 RPM, like traditional vehicles do, the hybrid system uses a much larger motor which spins the gas engine to a minimum of 800 RPM.  Then it waits until oil-pressure is established before injecting fuel and producing a spark.  This process enables a very smooth startup, reducing burden on bearings, pistons, and cylinders.

Another important fact to be aware of is the design of engine components. They were modified from traditional design (weight reduced, size reduced, etc.) to help make the startup process easier.


Motor needs electricity from the battery-pack.     back to top

Nope!  Motor propulsion is commonly supplied on-the-fly from the gas engine.

The engine creates electricity while you drive, 100% of the time thrust is be provided in fact.  Quite frequently, you'll see (on the Multi-Display) that the generator-motor is being fed directly from the engine without the battery-pack being used at all.  And sometimes, while both the engine and thrust-motor are providing power to the wheels, there's enough electricity remaining from the generator-motor to recharge the battery-pack at the same time.

Climb a steep hill sometime.  Observe how the charge-level of the battery-pack rarely drops as a result.  And if the conditions are right, you may see an increase to charge-level.  It can actually have more stored electricity available at the top of the hill than it did when you began the ascent from the bottom.


Short trips will result in low MPG.     back to top

What does "short" actually mean?

This misconception originated from the classic Prius.  To reduce emissions, the catalytic-converter must be hot for the cleansing of exhaust to occur.  The source of that heat was exclusively from the engine.  It required gas to be consumed just for the sake of getting the engine hot, so MPG would suffer during the first few minutes of driving.  The design is different with the new Prius.  Toyota added a 3-liter thermal storage container.  When you power-off the hybrid system, hot coolant (anti-freeze) is pumped into that thermos.  (It will remain hot overnight and warm for up to 3 days.)  Then later when you power-on the hybrid system, that hot coolant is pumped into the head of the engine.  Heat for the emissions system is available significantly faster than in the past.  That allows the engine to shut off much sooner, which saves gas.

When "short" is referred to, it is usually quite vague, since each person has their own interpretation based on their own traditional driving experiences.  For Prius, the Multi-Display reveals efficiency detail.  So owners quickly discover what "short" actually means.  For many, that is about 30 MPG on the first 5-minute segment shown on the "Consumption" screen.  And since both the engine & emissions system are usually still hot when you leave the destination of your short trip (grocery store, bank, retail store, mall, gas station), warm-up is reduced to almost nothing.  That first 5-minute segment on the drive home will be yield considerably higher MPG than on the drive there.

In summary, the impression some have of "short" trip MPG is rather misleading.


The cold engine is strained in the winter.     back to top

Just the opposite!

In the winter, not only does the engine have a chance to properly warm up, it actually gets a longer opportunity than in the summer.  The electric propulsion is favored even greater in cold conditions.  This is possible because there is much less of a concern about being able to keep the battery-pack cool.

The hot coolant stored in thermos is pumped into the engine head the moment you push the "Power" button.  So warming actually begins before the engine is even started.  That helps to reduce strain.  Then later when stressful thrust is needed, the motor works hard to prevent the engine from needing to provide much of it.  The engine just continues to run at a constant slow RPM to create heat.  As a result, energy is available for generating electricity.  And that's exactly what the system uses it for.  That, along with the battery-pack, feeds the electric-motor enough to protect the engine until it's warm enough to run like it normally does.

As a result of the special control for cold conditions, the engine isn't strained and warm up actually occurs surprisingly fast. 

In other words, the hybrid system offers an advantage that traditional vehicles cannot compete with.


Snow & Ice handling is a problem.     back to top

Not true, with respect to both hybrid components and the tires.

99 pounds is all the battery-pack actually weighs.  That's it, just a very small amount for a vehicle that weighs 2,890 pounds.  The little bit of actual extra weight is almost completely trivial in comparison to vehicle size.  Prius is bigger than Corolla (which weighs 300 pounds less) and smaller than Camry (which weighs 296 pounds more).  And remember, HSD doesn't have a transmission.  The Planetary-CVT is nothing both a set of power-carriers that all together are only the size of the palm of an adult's hand.  That design clearly eliminates quite a few pounds that are present on a traditional vehicle, but not on Prius.  In short, weight is a non-issue.

The tires are nothing special, just run-of-the-mill standard all-season radial tires.  In fact, you'll find them on a few other common vehicles too.  So they do an adequate job for the typical owner.  For those that desire increased traction, premium tires are available.  And upgrading to them is no big deal, since the size on the newer model Prius is fairly common.

Also note that the HSD system provides engine-braking (the "B" mode in Prius), something tradition vehicles do not.  When you shift to "B", the engine participates in deceleration.  The pistons pump (silently) under a compression load but without any fuel being consumed.  This provides a slowing ability without affecting the wheels at all, an obvious traction advantage when the road is exceptionally slippery. 


The brakes are more complicated.     back to top

No!  They are the same as traditional brakes.

The brakes are just plain, old, ordinary disc (front) and drum (back).  Any auto shop can repair & replace them.

Primary deceleration is provided by the electric motors, which are part of the transmission.  They are always engaged, a standard part of the propulsion system.  So no additional parts are needed for the braking ability.  Energy capture (regenerated electricity) begins when you lift your foot from the accelerator-pedal; slowing occurs by the 10kW motor spinning.  When you step on the brake-pedal, the 50kW motor takes over; this provides greater deceleration as well as more electricity.  Thrust beyond the standard tolerance for the large motor is handled by the traditional brake pads & shoes.  As a result of this setup, the brakes are used less than in traditional vehicles.  So they should last longer.

Emergency deceleration is provided exclusively by the traditional brake pads & shoes.  The abrupt pressure coming from the brake-pedal is automatically detected and the entire regeneration system is bypassed.  You can feel it too.  It's like slamming on the brakes in a traditional vehicle.

ABS (Anti-Lock Braking System) is a standard component within Prius, all packages include it.  The responsiveness is exactly like that in traditional vehicles.  So you'll retain control on rain, snow, and ice the same way you have with other ABS-equipped vehicles you've driven.


The heater won't be able to keep me warm.     back to top

Nope!  It works just fine.

It's actually surprising how much heat comes from the smaller-than-average engine.  But when you consider how important heat-retention is for the emissions system, it becomes clear that the Toyota engineers went to great lengths to prevent the engine from needing to restart... which includes having to keep the heater-core warm.

Owners living in northern climates like Minnesota have driven in extremely cold conditions (-15�F, -26�C) without any concern.  You even have the option of covering the radiator air intake for added heat.


The battery-pack will have to be replaced.     back to top

Life-Expectancy is 10-12 years (roughly 150,000 to 200,000 miles), which is long enough to fulfill the needs of most owners.

Warranty is 8 years / 100,000 miles.  So if replacement really is necessary beyond that time, production increases & competition should help to reduce the cost.  Continued technology improvements in energy density could too.  Additionally, the salvage market has already begun to emerge, allowing you to purchase a used battery-pack (or just some modules) recovered from a vehicle destroyed by an accident.

The most important aspect of battery-pack life is the fact that the HSD system doesn't allow the charge-level to ever reach low, since deep-discharging is a behavior that shortens battery life.  Unlike rechargeable batteries in cell-phones, notebook computers, handheld devices, MP3 players, children's toys, etc. that are all commonly allowed to be drained completely dead, the ones in Prius have the ability to recharge immediately.  The engine simply starts up whenever the charge-level drops to "Pink" (that's 2 bars) on the Multi-Display, which is about 40% capacity.  That process offers significant protection, a guarantee that life will be much longer than that observed in other products that use rechargeable batteries.

Also, note that after the rated 10,000 recharging-cycles have been used, the overall capacity of the battery-pack would have only been reduced to 80%.  So even at the point, the hybrid will continue to operate as it always had.  The only difference will be a reduction in efficiency.  The engine will simply have to run more.  That's it.

Lastly, it is very important to remember that the hybrid system prevents the battery-pack from being used as much possibly.  Much of the needed electricity (for non-stealth driving) comes directly from the engine instead, generated for immediate use.  Avoiding use of the battery-pack like that obviously helps to extend the life of it.


The battery-pack has to be recharged using a plug.     back to top

Never!  You never plug in the battery-pack.  In fact, there isn't even a plug available.

The ENGINE  provides electricity by igniting gasoline to rotate the generator-motor.  You can observe process this on the Multi-Display.  As you drive along, electricity is created whenever the engine is providing thrust to the wheels.  It's how the power-split device (Planetary-CVT) was designed to work.  The engine runs at an optimum RPM, to save gas.  Typically, that RPM is more than what is needed to propel the vehicle.  So any extra electricity that results is routed to the battery-pack for recharging.   This means the charge-level will usually remain high, even when climbing a hill.

The BRAKES also provide electricity.  This is done by using excess kinetic energy to rotate the generator-motor.  You can observe process this on the Multi-Display too.


Toyota loses money on each Prius sold.     back to top

Not anymore!  Of course, most new designs lose money when first introduced anyway.

It is true that Prius initially lost money.  Building the hybrid did cost more than it was sold for, at first.  But over the years, Toyota managed to overcome production expenses to reduce that cost to below the window-sticker price.  By late 2002, the THS design had proven so successful that Toyota decided to invest again.  That made Prius, once again, unprofitable.  Fortunately, the new HSD design was created for use in the entire fleet of Toyota passenger vehicles, every single model... which means it is quite inappropriate to place the entire burden of that research & development solely on just one vehicle, Prius.

Now in 2007, there are over 1 million Toyota/Lexus on the road.  Earning profit has become a realistic expectation.  The other automakers are joining in as a result.  The design has proven itself.  Losing money is just a memory from the past.


The battery-pack is harmful to the environment.     back to top

Thankfully, that's not the case.

NiMH (Nickel Metal Hydride) of the battery-pack is a environmentally benign substance.  It can be recycled too.  In fact, the guarantee for recycling is rather high since nickel is a valuable metal.  Toyota even offers a bounty to help ensure their recovery.  Misconceptions about rechargeable batteries typically stem from the obsolete NiCd (Nickel Cadmium) technology, which actually is harmful.


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