Skip to Content

Does O/D OFF Make Your Car Faster?

Does O/D OFF Make Your Car Faster?

Overdrive (O/D) was a common feature in most automatic transmission vehicles of the late 20th and early 21st century.

Its popularity is gradually fading as more automobile manufacturers adopt better, modern transmissions that have higher gearing to improve cruising and better fuel economies. 

If you own an older automatic vehicle, the chances are that it has an O/D button on the side or front of the gear lever. What is its role? 

Many drivers mistake the meaning of the term overdrive to mean that their cars are “overdriving” or driving at higher speeds, hence better performances. However, that’s not the case. And, does it make your car faster?

O/D is the highest gear in a four-gear transmission that improves transmission efficiency over performance. Keeping it OFF prevents acceleration beyond a certain RPM, hindering your car from achieving maximum speed output. Basically, O/D OFF sacrifices top speed to allow your vehicle to drive on lower gears, meaning it does not make your car inherently faster.  

What’s Overdrive (O/D) in a Car?

Overdrive is a feature on most vehicles that reduces the engine’s revolutions per minute (RPM) at sustainable higher speeds, resulting in improved fuel economies, lower noise, and less wear. 

Basically, it’s the highest gear that a car can run on while cruising at highway speeds (typically higher than 50 miles per hour).

Overdrive is beneficial to the vehicle in the long run, as it reduces the wear and tear that occurs during gear changes.

You can use the overdrive function on every gear, but that wouldn’t make any sense.

Most car transmission systems lock (keep it OFF) it until the higher third or fourth gears to prevent engine lug every time a gear change occurs.  

In overdrive, you will have a greater transmission shaft speed compared to the speed input of the engine’s shaft.

In other words, your car maximizes on a specific torque and sacrifices top speed and performance to give you a good cruising speed that’s fuel and transmission friendly. 

Take underdrive as an example. The engine shaft will rotate at a higher speed than your car in an underdrive.

The transmission gear transfers a lesser speed to the driven shaft or than the speed of the normal gears. 

When to Use Overdrive/ Turn Overdrive ON

Overdrive is beneficial in automatic transmission cars when you’ve achieved cruising speeds.

In older cars, it was a feature that was automatically turned on, and you would press an O/D button on the gearshift joystick to turn it OFF. 

Keeping your car in overdrive is very beneficial as you’ll spend less on fuel and maintenance.

Driving at highway speeds of more than 50MPH forces the engine to run faster and consume more fuel.

If you activate the overdrive function, your car will maintain the same speed, but at a lower RPM. 

In effect, the engine experiences less strain and consumes less fuel per mile. Keeping it ON gives you a smoother and more relaxed trip than when it’s turned OFF. 

In newer cars, the overdrive feature is more sophisticated and controlled by your car’s Electronic Control Unit (ECU) to automatically activate or deactivate when necessary.

If you do a lot of highway travels or don’t carry cargo close to your car’s payload, it’s more effective to keep the O/D ON.


When to Keep Overdrive OFF

As we’ve seen, O/D is only beneficial when you want to keep your car at cruising highway speed while using less fuel.

When you’re not cruising, it’s better to turn it OFF. Here are some situations that may force you to turn the overdrive OFF.

When Driving Up a Steep Hill

When going uphill, you will want to keep your car in a lower transmission gear to utilize the high torques that come with lower gears.

However, turning O/D ON or OFF depends on the size of your vehicle’s engine, its payload, and the state of its drivetrain. 

If it’s a modern automatic vehicle, it will shift out of overdrive automatically when it detects that it’s underpowered.  

When Towing or Carrying Heavy Loads 

Similarly, towing puts a car’s engine under massive stress. And since overdrive locks a vehicle at higher (third or fourth) gears, the torque shall be insufficient to allow the car to drive at the same speeds. 

You’ll immediately feel that the car is underpowered, and you might have to turn overdrive OFF.

If you prefer towing while the O/D function is ON, do so on flat or gently sloping roads that require less power to navigate. 

Towing on steep hills and bumpy roads will bog your engine down and cause it to degrade faster.

You can also end up overheating the transmission and causing damage to the drivetrain.  

Advantages of Using the Overdrive ON Function 

Since the early 1980s, more and more vehicle manufacturers have incorporated better overdrive functions to improve their fuel economy ratings.

However, advancement in transmission means that the feature is losing popularity amongst car enthusiasts. 

Modern-day vehicles have more gears between the first and the last gears, resulting in a smoother drive.

Still, having an overdrive function in your car is beneficial for the following reasons.

  • It improves your vehicle’s fuel economy
  • Lowers engine and transmission wear
  • It improves your vehicle’s overall life as it won’t strain engine-related accessories such as pumps and alternators

Final Words For Using O/D

With increasing automation in the automotive industry, features such as adaptive cruise control (ACC) and cruise control are quickly replacing the overdrive function.

But the O/D is still present and important in most modern-day vehicles. It doesn’t make you drive faster, but it drives more economically.

In conclusion, you may want to turn OFF the overdrive feature before overtaking the vehicle in front of you.

Dropping to a lower gear allows you to increase your vehicle’s RPM, causing it to be more responsive. 

Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!