What Is The B Mode On The Prius Shifter? B Gear Meaning

By Dan Ross

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Labeling different driving modes in capital letters is a common trait for numerous hybrid vehicles – and the Prius Shifter is no exception. As such, it is natural for inexperienced drivers to get confused about the B shift on Prius: what exactly does it mean?

My guidelines offer to discuss this mode in more detail. Keep scrolling.

What Does The B Mean in A Prius

The letter “B” on the Prius shifter signals “Brake” modes, similar to when shifting to lower gears to slow down and stop the car. It’s usually applied when descending, and the engine will produce electricity for braking rather than you hitting the brake pedal, hence less wear.

B Gear Prius

Since hybrids use both gasoline engines and electric motors for vehicle power, the shifter (or gear selector) is implemented to let drivers switch between separate modes – “Brake” or “B” also included.

Specifically, as the “B” mode is engaged, the car will switch to electric-based propulsion to reduce excess workloads/pressure on the car’s gasoline engine. 

Plus, the Prius also engages in regenerative braking (as the name “Braking” clearly suggests) to capture the brake’s energy and store it within the battery. As such, energy efficiency significantly increases, further extending the battery’s mile life.

The Pros and Cons of The B Gear Prius

The B mode keeps your braking system at peak conditions and reduces the need for frequent maintenance. It works great during downhill slopes and even recharges the battery during the process. However, excessive usage might lead to battery strain, reduced fuel economy, and skidding accidents.

1. The Pros

a. Great for Downhill Driving

As a rule of thumb, the car may spiral faster than expected as it starts heading downhill. 

Rather than engaging the brakes, Prius B gears can be your lifesaver here: its reliance on electric motors allow safe and constant speed maintenance without the excessive drag resistance often seen in conventional brakes. As such, you will land safe and sound.

b. Great for Battery Recharging

Unbeknownst to some, engaging the B mode is one of the greatest ways to charge your battery. 

If you do not believe me, just try out: switch to the “B” mode when your batteries are below 100% full, and they will start recharging immediately.

Regenerative braking is the magic word. As you coast/brake, the electric motors that usually take charge of wheel driving are changed into generators for energy reclaim instead. 

They change the car’s kinetic energy (created by friction) into energy-creating sources – a feat only possible for hybrid cars like Prius. On regular vehicles, this energy will get absorbed by the heat and eventually vanish.

Better yet, the gasoline engine does not stay out of the process; it also helps charge the batteries during drives. You can compare their mechanisms to alternators and starting batteries.

c. Reduced Need for Regular Car Maintenance

As established above, the B mode ensures no brake engagement is required – which means your brake pads and rotors enjoy fewer workloads and clearly always remain at peak condition.

Hence, you no longer have to drive to the automobile shop every few thousand miles to have the brake system components checked and upgraded by experts.

As defects, overheating issues, and all other common premature brake wear are dramatically lessened, imagine how much money and effort you could save in the long run.

2. The Cons

a. Increased Fuel Consumption

The “B” mode engagement reorders the entire engine timing, forcing the gas engine feature to function as the brake now. 

Hence, the engine drags are increased, eating up more fuel than usual. And worse, inexperienced hybrid drivers often fail to notice the drop until they go to the gas station.

b. More Battery Strain

As mentioned above, activated B gears mean the batteries also get charged. While that sounds great, imagine it happens when the batteries are already full or nearly full.

In those cases, the batteries do not receive any extra energy. On the contrary, they even suffer from excess strain and brake pressure, eventually failing to hold a charge. 

c. Skidding Accidents

Accidents like these often occur when the B mode is suddenly engaged amidst intense high-speed drives or acceleration. Thus, always lower your vehicle speed first before changing to B to prevent jerky transitions. 

When Should You Use and Not Use It?

use B Gear Prius

The B mode’s advanced braking force and additional torque will be helpful for steep descents, icy conditions, heavy loads, or when your car has broken wheel issues. 

But do not use them in normal driving. There is no point engaging them when they are not needed, and not to mention, too much usage does more harm than good to the car’s fuel economy.

How to Use The B Mode on Prius?

Reduce the car’s speed to avoid skidding accidents. Once getting comfortable with your speed, use the car’s gear shifter to switch to “B” mode (you do not have to apply the brake during the process). 

Your engine will give off a loud rev sound, informing you that the B gear is officially engaged. 

If you want to disengage the B mode, simply touch the shifter and switch to another mode. 

D or B Mode: Which Is More Efficient? 

There is not really a better option: D modes tend to falter slightly during critical situations (downhill grade or icy situations), while B modes may over-brake and slow the car unnecessarily. 

When at their peak performances, their speed profiles are identical and seasoned drivers barely spot any difference. Hence, things boil down to your styles, preferences, and driving situations.

Can You Switch From D to B While Driving?

Yes. Actually, that is the only way you can change to B mode. Hybrids do not allow drivers to switch from P (park) to B, though the reverse (from B to P) is still possible.

Still, when there are loud engine revving sounds, chances are the B mode is being overworked; switch back to D immediately.

What Is The Prius’ Maximum Speed Limit When In B Mode? 

So far, there has not been any official upper limit for the B gear, though some drivers do advise not to engage the mode at any engine speed below 65 MPH to err on the safer side.


As explained throughout my article, B on a Prius shifter refers to “Engine Braking Mode” – a driving system strongly recommended for downhill roads or icy terrains. 

Only switch to B from your D (driving mode), and refrain from using it in regular driving or when it is not really needed.

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