Should You Use S Gear or D Gear on the Highway?
4 Answers
When driving on the highway, using D gear is sufficient because D gear is the forward driving gear of the car. Whether on the highway or during daily commutes, D gear can meet the power demands of the car in most road conditions. Here are the relevant details: Reasons for using D gear on the highway: Once the car enters the highway, it doesn't require frequent rapid acceleration or deceleration like on city roads, and it mostly maintains a speed of 90-120 km/h over long distances. As a result, the car drives relatively more smoothly. Additionally, D gear optimizes the operation of the transmission based on the car's driving conditions, making the car more fuel-efficient. Therefore, D gear is suitable for use on the highway. S gear: S gear is the car's sport mode and can also be considered a forward driving gear like D gear, but it represents a different mode within the same mechanical structure. When shifting into S gear, the car's gear shift timing is delayed, causing the engine to operate at higher RPMs for a longer duration. This keeps the car in a low-gear, high-RPM state, resulting in greater output torque. Thus, S gear is more suitable for situations where the car needs increased power.
On highways, I mostly drive in D mode, which is the most fuel-efficient and hassle-free option. The car automatically controls the gear shifts to maintain an economical engine speed. When overtaking or climbing a slope, I switch to S mode, which delivers noticeably stronger power, making it more confident to pass trucks—though S mode comes with louder engine noise and higher fuel consumption. Switching between modes on the highway is simple—just push the gear lever—but avoid constantly driving in S mode at high speeds, as it’s not ideal for the transmission. My experience is that D mode covers 90% of driving needs; it just depends on whether you prioritize fuel efficiency or a bit of driving excitement.
On the highway, I prefer using D mode as it provides the most comfortable cruising experience. Modern cars are smartly tuned in D mode, maintaining low and quiet engine RPM at 120 km/h while keeping fuel consumption under control. I mainly use S mode when quick power is needed, such as overtaking buses or accelerating before entering tunnels. However, avoid prolonged use of S mode as the engine stays at high RPM, which can lead to overheating. The dashboard shows at least 10% higher fuel consumption in S mode. Once during a 500 km test drive, D mode saved me nearly a liter of fuel compared to S mode. So for long highway trips, sticking with D mode is the most economical choice.
Gear selection on highways depends on driving habits. D mode is suitable for regular cruising, with the transmission automatically upshifting for smooth power delivery and low fuel consumption. S mode delays shift timing, keeping RPMs in the 3,000-4,000 range, making overtaking and acceleration particularly exhilarating. I've tested both on highways - accelerating from 80 to 120 km/h, S mode is 2-3 seconds faster. However, prolonged high-RPM operation in S mode increases engine carbon buildup risk. Recommended to switch based on road conditions: use S mode for flexible response in heavy traffic, and switch to D mode for cruising in light traffic to protect your vehicle. Try both modes yourself to understand the difference.
