What is the primary function of an engine brake?

The primary function of an engine brake is to assist in reducing vehicle speed. When an engine brake is engaged, it uses the engine's compression to create resistance, which slows the vehicle down without relying solely on the traditional braking system. This is particularly beneficial in situations like descending steep hills, where controlling speed is critical to maintain safety and avoid overheating of the standard brakes. By using engine braking, the driver can enhance vehicle control and reduce wear on the braking system.

While increasing engine power, optimizing fuel efficiency, and improving engine performance are important aspects of engine function, they do not accurately describe the main purpose of an engine brake. The braking action provided by the engine is what distinguishes it from other functions related to power and efficiency.