What is the function of the engine tachometer?

[MacDakota]

The function of the engine tachometer is to monitor the working status of the engine. Ignition phase: A four-cylinder gasoline engine generally needs to reach about 80 revolutions per minute (rpm) to ensure successful ignition, but in practice, the speed is usually increased to 120 rpm to guarantee ignition quality. Without a tachometer, you wouldn't even know if the engine has a problem. Start-up moment: At the moment of engine start-up, the speed often reaches 1200-1500 rpm, and even higher in cold weather. However, the speed during cold start should not be too high because the lubricating oil hasn't reached the upper part of the engine yet. To reduce wear, it's best to keep it below 2000 rpm. Gear shifting timing: The tachometer can also indicate the optimal time for manual transmission gear shifting. Generally, shifting at around 2500 rpm is the smoothest and most fuel-efficient. If more power is needed, shift above 3000 rpm.