1. Unnecessary Wear and Tear: Constantly shifting from Drive to Neutral and back to Drive puts additional strain on the transmission components, such as the gears and synchronizers. Shifting frequently can cause premature wear and tear of these parts, eventually leading to costly repairs.
2. Reduced Safety: Keeping the transmission in Drive allows your vehicle to be ready to react quickly in case of any sudden traffic movements. Leaving the car in Neutral can give a false sense of control, as the wheels are no longer connected to the engine's power. If you need to accelerate or move suddenly, you'll lose valuable seconds to shift back into Drive, which compromises your safety.
3. Fuel Efficiency: Engaging Neutral at traffic lights does not improve fuel efficiency, as previously believed. Modern vehicles' fuel injection systems and computers effectively manage fuel supply, and stopping in Drive with your foot on the brake does not consume significant fuel. In fact, frequently shifting in and out of Drive may disrupt the vehicle's fuel efficiency pattern.
4. Transmission Cooling: Leaving the car in Drive allows it to remain in gear. The vehicle's cooling system circulates transmission fluid while in gear, ensuring proper and effective cooling of transmission components. Shifting to Neutral interrupts this flow, which can cause components to overheat, especially under sustained heavy traffic conditions.
5. Roll-Back Risk: Some vehicles, particularly those lacking hill-hold mechanisms, tend to roll backward when stopped on sloping road sections. Keeping the transmission in Drive engages the parking pawl, locking the driveshaft, and keeping your vehicle securely in place. Shifting to Neutral will leave you unprotected.
Remember, modern automatic transmissions are carefully designed for both smoothness and fuel efficiency. They engage a lower gear when braking and return to the appropriate gear for a smooth start. It's most efficient to let the automatic transmission do its job in maintaining the ideal gear, rather than manually shifting.
