What is the primary reason to use low gear when descending a steep slope?

When descending a steep slope, using low gear is primarily important for utilizing engine braking, which helps maintain control of the vehicle. In low gear, the engine is engaged in a way that creates resistance against the vehicle's natural tendency to accelerate due to gravity. This resistance slows the vehicle down without relying solely on the brakes, which can prevent overheating and provide greater overall control during the descent.

While maximizing fuel efficiency, navigating turns, and reducing tire wear are important considerations in driving, they do not directly relate to the critical task of safely managing speed on steep declines. Using low gear effectively enhances safety by ensuring that the driver can control the descent and manage the vehicle's speed more reliably under the challenging conditions of a steep incline. This practice is essential for preventing brake failure and ensuring that the driver can respond effectively to sudden changes in the driving environment.