Improvements in the engineering and design of Mercury clutches have made it possible for most clutches to last more than 80,000 miles, compared to the norm of 50,000 to 60,000 miles that was seen in cars through the 1970s. Some of the new technology improvements in clutches can be seen in the friction materials used to build the clutch components, and updates in the pressure plate, including centrifugally assisted diaphragms. Some of the new extremely strong units are made from steel or high-grade aluminum alloy. Those improvements are key to making a long-lasting clutch, since the constant heat and friction that Mercury clutch components endure will eventually wear down on them. The Mercury clutch works to help the engine's spinning parts engage - or disengage - with the turning wheels. The clutch acts to join or disconnect the transmission from the car's wheels, and is activated by the pressure of your foot on the pedal. Eventually, the friction will wear down the friction materials, until the surface is too thin to transmit enough torque to move the car normally. At that point, you will begin to feel and hear signs that your Mercury clutch is failing. You might struggle to release the clutch, or notice slipping, 'chattering,' or hideous screeching. Sometimes the car will flat out refuse to move at all when the Mercury clutch is dying. Before the noise begins, there might have been some early signs that the Mercury clutch is failing: poor gas mileage. When you go up hills, you need to downshift more often. All these are signs that your Mercury clutch is ready to die an honorable death - and needs to be replaced.