What gear should an automatic car use when going downhill?
2 Answers
Automatic cars need to adjust the gear selection based on the steepness of the slope. Use lower gears for steeper slopes and higher gears for gentler slopes. Below are relevant explanations: Methods for controlling speed: For manual transmission cars facing long or steep downhill roads, you can shift into D2 or D3 to control the gear. D2 means the transmission won't shift beyond 2nd gear, while D3 limits it to 3rd gear. This allows full utilization of engine braking to effectively control vehicle speed. Principle of engine braking: Engine braking refers to the drag effect created by the compression resistance, internal friction, and intake/exhaust resistance generated during the engine's compression stroke on the driving wheels (manual transmission cars can be parked on slopes while in gear using this principle).
I've been driving automatic transmission cars for over a decade, and the safest way to handle downhill slopes is to use lower gears, such as shifting to L gear or manual mode's 1st or 2nd gear. This is because the engine assists in braking and deceleration, reducing wear from frequent brake usage. Especially on long steep slopes, continuous braking can cause brake discs to overheat and fail, potentially leading to accidents. Once when driving on mountain roads, I neglected to use lower gears and ended up with smoking brakes—fortunately, I didn't lose control. Now, I always slow down and shift gears in advance, which not only protects the braking system but also saves fuel. Different car models may have different gear names; for example, S gear is also a good option—check your owner's manual to familiarize yourself with your vehicle. In terms of safety, controlling speed downhill is crucial, and developing this habit is absolutely worthwhile.
