Engine speed refers to how fast an engine is running, typically measured in revolutions per minute (RPM). This measurement indicates the number of times the engine's crankshaft completes a full rotation in one minute. Higher RPM values usually mean the engine is working harder, which can lead to increased power output but may also result in higher fuel consumption and wear on engine components. Monitoring engine speed is crucial for optimizing performance and efficiency. In vehicles, the tachometer displays the engine speed, helping drivers understand when to shift gears for better acceleration or fuel economy. Maintaining the right engine speed can enhance the lifespan of the engine and improve overall vehicle performance.