JustAnswer Blog: Automotive

You are here

What does overdrive do?

This is a great opportunity for overdrive

This is a great opportunity for overdrive

What does overdrive do?

Tristan Hoag

By Tristan Hoag on May 24, 2018

It may be great for fuel efficiency, but what does overdrive do in the wrong situation?

As more traffic moves onto highways and picks up speed, auto manufacturers have had to keep up with the demands that those higher speeds place on the engine. The need to balance this demand for performance with increasing standards for fuel efficiency is one of the defining challenges in automotive design, and has led to beautiful inventions like overdrive.

What does overdrive do, you ask? Good question!

The automatic transmission in your car works by switching gears in response to the way you drive, changing how much power is delivered to the wheels. When you accelerate or climb a hill, a lower gear will deliver more power from the engine, and while you’re cruising, a higher gear allows the car to maintain speed without working as hard. By reading the position of the gas pedal and the amount of engine strain, it reads the demand and shifts gear accordingly.

Overdrive is the highest gear in your automatic transmission, and it’s intended to lower the RPM of the engine to the most fuel-efficient level required to maintain the desired speed. While in overdrive, the vehicle will find the most efficient gear to cruise in at higher speeds. This means less fuel is required to maintain that cruising speed, and you’re putting less strain on the engine in the process.


Making the best use of overdrive

To get the best performance out of your overdrive gear, you should use it when you’re driving at higher speeds, above 50 mph, on reasonably flat and smooth roads.

The advantages of using overdrive include:

  • Increased fuel efficiency: Because the engine turns over more slowly, you’re using less fuel to maintain speed.
  • Decreased engine strain: Fewer rotations per minute mean less pressure on the engine, slowing wear and keeping engine temperature lower.
  • Carefree driving experience: Because of the nature of automatic transmission, all of the adjustments happen without you needing to think about them. All you have to do is drive, and the efficiency takes care of itself!

If your car has an overdrive gear, you’ll have a dedicated overdrive button, but the button actually turns off overdrive mode. Overdrive is a useful enough mode that it stays on until you turn it off which should give you an idea how much the manufacturers expect it to be used.

Since overdrive is the highest gear, when you turn it off you’re denying the vehicle access to the most efficient gear. But if it’s so efficient, why would the manufacturers give you the option to turn it off in the first place?


When not to use overdrive

When you’re using overdrive, automatic transmission will switch between all of the gears to find the most efficient one. This works well when your vehicle is driving at reasonably high speed on smooth roads. It’s not as much of an advantage when you’re driving under more strenuous conditions.

Some of situations when the overdrive gear can be a problem include:

  • Low speed: At speeds under 50 miles per hour, overdrive can start hunting for the most efficient gear, shifting frequently. This can be annoying and puts wear on your transmission.
  • Hilly terrain: The engine strain from climbing steep hills can confuse the overdrive, and it’s a best practice to downshift when going large hills so the engine keeps your speed low and you can minimize brake use. Turn off your overdrive in these situations.
  • Towing: If you’re pulling a trailer or otherwise hauling a heavy load, you should turn off your overdrive.

Avoid using overdrive in stop-and-go traffic, or in difficult terrain, and you’ll be fine. Otherwise, turn it on as soon as you get up to speed!

The face of fuel efficiency has changed a great deal since 1916

The face of fuel efficiency has changed a great deal since 1916

Dangers of incorrect overdrive usage

With great fuel efficiency comes great responsibility.

No technology is perfect, and overdrive is no exception. There are consequences to using overdrive incorrectly. When you leave your overdrive on in the situations described above, it will burn out your transmission fast. This will be a costly repair, running to thousands of dollars, that will more than offset the savings you might have gained through fuel efficiency.

Learning how to read your situation and make the best use of overdrive will allow you to get the best life from your transmission, and the best fuel efficiency from your vehicle. Check your owner’s manual to see if your vehicle has an overdrive gear, and any specific instructions for optimal use.

When you want fast answers to automotive questions such as “What does overdrive do?”, you can wait to schedule a visit with a mechanic, or you could turn to the automotive Experts on JustAnswer. Whatever your problem, they can help you find a way to resolve the issue yourself, or send you to the mechanic armed with knowledge.

Have you had problems with the overdrive in your car? Share your story in the comments below!