D3 is a specific mode that you can shift to in some automatic transmission cars (typically Honda) that is useful for driving down steep hills, driving in stop-and-go traffic, or driving on slippery roads.
What does D3 mean on an car?
Selecting D3 with the shift lever of an automatic car limits the transmission to only use the first three gears. This provides greater control of which gears your car uses, rather than letting the computer choose the gear.
Using D3 can be beneficial under certain driving conditions such as:
- 1. Selecting D3 uses engine braking for driving down steep hills. This can reduce wear on brakes and brake pads.
- 2. Selecting D3 in stop-and-go traffic will prevent the car from shifting into higher gears, which will consume less fuel.
- 3. D3 is recommended when towing a trailer on hilly roads.
You can check the owner’s manual for specific instructions on when to use D3 for your specific model.
Only some car models have a D3 selection available on their shift lever. In many modern cars, the car relies on the computer to determine the optimal gear.
What is the difference between D3 and D?
When “D” is selected, the car automatically shifts into the optimal gear based on the current speed and acceleration.
In “D” mode, the car may even shift into higher gears to warm up the engine faster in cold weather.
When “D3” is selected, the car will automatically shift between the first three gears, but will not shift to a higher gear.
How to shift to D3
Typically, you will let your foot off the acceleration and move the shift lever to the D3 selection. Some cars have a button on the shift lever for D3 mode (an example of this is the 2009 Ridgeline).
Avoid pressing the acceleration pedal at the same time as shifting, as this could damage the transmission.
When not to use D3 while driving
Under normal driving conditions, it is usually best to use the “D” gear selection rather than D3.
D3 is not ideal for normal highway driving, as the engine will have a higher RPM at the lower gears and consume more fuel.
D3 should not be used when towing a trailer on normal road conditions, as this can cause an increase in transmission fluid temperature and cause overheating (source: 2009 Honda Ridgeline owner’s manual).
How does D3 affect maximum speed?
A car in D3 mode is not able to reach its top speed because it is limited to the first three gears.
For example, a Honda Civic EX has a maximum speed of 112 when D3 is selected.
How does D3 affect fuel efficiency?
Using D3 can have a negative effect on fuel efficiency since the car will be limited to using the first three gears and will not be able to shift to higher gears at high speeds.
Cars with a D3 Selector
The D3 selector is common on older Honda models. In newer models, the D3 mode has been replaced by “S” and “L”.
Some examples of cars that have a D3 selector are the:
- Honda Civic
- Honda Ridgeline
- Honda CR-V
- Honda Pilot