Which gear should be used for automatic transmission cars on highways?

[JeremiahLee]

For automatic transmission cars on highways, the D gear is used. The specific reasons are as follows: 1. The D gear is usually the forward gear, and acceleration is performed according to the set program for upshifting, which is relatively more fuel-efficient. It is recommended not to use the S gear for long periods on highways, as the S gear only delays upshifting without changing other working conditions, which will inevitably increase the transmission load and temperature in a short time, leading to accelerated wear. 2. Moreover, the comfort of the vehicle in S gear mode is slightly worse, so try to avoid using the S gear for extended periods. The D gear is the forward driving gear used in most automatic transmission cars, with some designed with a sequence from 1st gear to high gear, and others from 2nd gear to high gear. When driving, simply place the gear lever in the D gear, and the speed of the car will be controlled by the throttle.

[OZachary]

Driving an automatic car on the highway is quite hassle-free, mainly using the D gear is sufficient. When I go on long trips, I prefer to turn on the cruise control on clear stretches, which gives my right foot a good rest as the car maintains the set speed automatically, and the fuel consumption becomes more stable. When overtaking, don’t hesitate—just press the accelerator firmly to let the transmission downshift automatically, and the thrilling acceleration kicks in instantly. However, be cautious when encountering continuous downhill sections, such as entering mountainous areas. I switch from D gear to S gear or manual mode’s lower gears, allowing the engine to assist with braking and preventing the brake discs from overheating. Most importantly, always keep an eye on the temperature gauge. If you notice reduced power during uphill climbs, remember to shift to lower gears to protect the transmission.

[CalebLee]

Using D gear is the most comfortable for highway driving, as the transmission will automatically find the appropriate gear. However, I'm used to stopping at service areas every two hours to rest and check the car's condition. If encountering steep slopes, switching to manual mode and shifting to a lower gear is very effective—it saved my brake system last year when driving through the Yunnan-Guizhou Plateau. I usually only use cruise control when there are few cars around, as frequent acceleration and deceleration can actually waste fuel. Don’t hesitate to step on the gas when overtaking; modern automatic transmissions respond quickly to downshifts. By the way, some cars come with a sport mode, but it's unnecessary for long-distance driving as it significantly increases fuel consumption.

[Russell]

D gear is the main choice for high-speed driving, but I always keep an eye on the tachometer. Most cars maintain the most fuel-efficient RPM around 2000 when cruising at 80-120km/h. Downshifting before climbing long slopes can avoid frequent gear changes – that's how we tackle the winding mountain highways here. For overtaking, just floor the accelerator to trigger forced downshift. I remember driving a CVT car once, switching to simulated gears made downhill driving exceptionally stable. Sports mode is both fuel-thirsty and noisy, not recommended for long-distance trips.

[JuliaMarie]

Transmission engineers will tell you that the torque converter is locked in D gear at high speeds, equivalent to direct drive, achieving maximum efficiency. However, when encountering road sections with gradient changes exceeding 3%, proactive intervention is recommended: use manual mode to downshift by 1 gear when going uphill, increasing RPM by 10% to enhance power output; engine braking is safer for downhill sections. Pay close attention to the transmission oil temperature gauge—if it exceeds 120°C after consecutive overtaking maneuvers, it's time to take a break.

[VonColin]

We girls care more about comfort on the highway. Maintaining cruise control at around 110km/h is ideal, using D gear with the distance keeping function is particularly worry-free. Overtaking actions should be more decisive, as the pressure on the accelerator directly affects the downshift speed. The paddle shifters behind the steering wheel are actually very convenient, making downshifting and deceleration especially smooth when entering or exiting service area ramps. Keeping some cooling oil handy can prevent drowsiness, and it's essential to take a break every three hours—safety is more important than anything else.