Which brake system of a motor vehicle functions without any appreciable wear?

Both the engine brake and the retarder are braking systems that work without noticeable wear, because they do not rely on friction surfaces like brake pads or discs. The engine brake works by using the engine’s resistance to slow down the vehicle, while the retarder is a special device—often used in heavy vehicles—that slows the vehicle by generating resistance, usually through electromagnetic or hydraulic means. Both systems help reduce wear on the main braking system. In contrast, the compressed air-braking system operates traditional friction brakes, which do wear down over time. So, selecting both the engine brake and the retarder is correct. This is important knowledge, especially for driving large vehicles, since using these wear-free systems helps preserve the primary brakes and increases vehicle safety.