Which instrument displays engine speed in revolutions per minute?

A tachometer is the instrument specifically designed to measure and display engine speed in revolutions per minute (RPM). This is crucial for monitoring engine performance, as it helps operators understand how fast the engine is running, which can be important for maintaining optimal performance and avoiding engine damage.

In contrast, a speedometer measures vehicle speed and indicates how fast the vehicle is traveling on the road, which is not the same as engine speed. An odometer tracks the total distance traveled by the vehicle over time, and a fuel gauge shows the level of fuel in the tank. None of these instruments provide information about engine RPM, making the tachometer the clear and correct choice for displaying engine speed.