What does the OverDrive button do?

We often see a small button in some cars with an automatic transmission that wrote O/D, placed close to the transmission lever. If we pressed this button, the O/D OFF car indicator light on the dashboard would light up. Meanwhile, the O/D OFF car indicator light will go out if we do not push the button.

So, what does the O/D OFF car indicator light's on the dashboard panel mean, and what does it do? O/D on the automatic transmission car stands for Over Drive. This indicator light labeled O/D OFF will show how the automatic transmission will work regarding the number of acceleration gears used for driving and road conditions.

Errors in activating the overdrive button will impact fuel consumption and car acceleration that do not match expectations. Here is what the overdrive (O/D) button does and its effect on automatic cars.

The OverDrive (O/D) Button Function

The primary function of the O/D button is to activate or deactivate the Overdrive feature on the automatic transmission. This Overdrive feature will affect the number of acceleration gears used in the automatic transmission.

Suppose the automatic transmission has four forward acceleration gears. In that case, the gear used is only up to 3rd gear when the O/D OFF light is on. Meanwhile, when the O/D OFF light goes out, the gear used can reach the 4th gear.

When we use the O/D feature, the output speed of the engine will be faster than its input speed. Anyone who loves high-speed cruise control and good fuel economy will benefit from the overdrive gear.

When OverDrive is ON (O/D ON)

When the overdrive feature is active (O/D ON) and is marked with the O/D OFF indicator light off, the gearshift on the automatic transmission can reach the highest available gear. For example, the automatic transmission has four forward acceleration gears, so the 4th gear on this automatic transmission will use entirely.

When overdrive is active (O/D ON), the effect will impact engine power, the speed obtained, and the fuel consumption. If used on the freeway, the car can reach its top speed so that the engine speed is not forcing too high, increasing fuel use efficiency.

Therefore, O/D ON is very suitable to be activated when the car is driving on a smooth freeway. The OverDrive system will set the engine rpm at low speed to shift automatic transmission gears so that the engine is more fuel-efficient.

Here are some conditions that are obtained when O/D is ON

Automatic transmission gear shifts will feel faster because it occurs at low engine rpm.
More fuel-efficient when used on flat and barrier-free road conditions
Car acceleration is not very responsive compared to O/D OFF, so it feels the car is less powerful and less suitable for uphill or downhill roads.
No engine brake effect, so it is not suitable for use on downhill terrain.

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When OverDrive is OFF (O/D OFF)

When the overdrive feature is deactivated (O/D OFF) and the O/D OFF indicator light is on, the OverDrive system will set the gearshift on the automatic transmission one gear below the highest gear.

As in the previous example, for an automatic transmission with four forward acceleration gears, the maximum gear used in the automatic transmission is only up to 3rd gear when the overdrive is in the OFF position.

The effect obtained when the overdrive is turned off (O/D OFF) is that the engine speed used as the basis for automatic gearshift will be higher than when O/D is ON. Therefore, by disabling the overdrive function, the automatic gearshift process will occur at higher engine speeds, increasing the torque produced.

Here are some of the effects and conditions you get when O/D is OFF

The automatic transmission gearshift feels slower because the shift is set at a higher engine rpm than when O/D is ON.
It is suitable for use on roads with uphill or downhill terrain because it can provide an engine brake effect that can help the braking system.
Acceleration and engine power will be higher, so the car feels more responsive and comfortable to use when overtaking other vehicles.
Fuel consumption can be more extravagant if used on a flat freeway because of engine power that is restrained by the position of this automatic transmission gear.