In what situation is it recommended to use the engine brake?

Using the engine brake is recommended when descending steep hills because it helps control the vehicle's speed effectively while reducing the reliance on the brake pads. By engaging the engine brake, the driver utilizes the engine's resistance to slow down the vehicle, which helps prevent overheating and fading of the brakes. This is especially important on long downhill grades where continuous use of the service brakes can lead to brake failure, posing a significant safety risk.

In contrast, using an engine brake in heavy traffic might not always be practical or necessary, as it does not provide the fine-tuned control needed for frequent speed adjustments. Similarly, on flat roads, there is typically no need to engage the engine brake since the vehicle is not under the same speed control demands as when descending a hill. Parking on an incline can involve different techniques, such as using wheel chocks or the parking brake, rather than relying on engine braking alone. Thus, the context of steep hill descents highlights why it's the most appropriate situation for employing engine braking.