True or False: The use of brakes on a long, steep downgrade is only a supplement to the braking effect of the engine.

The statement is true because when descending a long, steep downgrade, the primary goal is to maintain control of the vehicle without overheating or overusing the brakes. Engine braking, or using the engine to slow down the vehicle, is the primary method recommended for reducing speed during such descents. This is particularly effective because it allows the vehicle to slow down without the risk of brake fade, which can occur with excessive use of the brake system.

While brakes are indeed used during a downgrade, they should be viewed as a supplementary measure. The engine's braking effect is often sufficient to control speed, especially when combined with downshifting and proper use of the accelerator. Relying mainly on the brakes in these situations can lead to increased wear and potential failure of the braking system, especially in heavy vehicles, which is why engine braking is emphasized as the first line of defense on steep grades. Overall, understanding this fundamental principle is crucial for safe driving in challenging conditions.