The number of engine operating hours is measured by the:

• A. Engine running time meter
• B. Hour meter
• C. Tachometer
• D. Fuel gauge

Answer: (A)

Measuring how long an engine has been operating is done with an engine running time meter, often simply called an hour meter. This device records the total elapsed time the engine has been running, which is exactly what you need to track for maintenance intervals and wear over time. Maintenance schedules are typically based on runtime hours because engine wear correlates with how long it’s been running, not just how fast it’s going or how much fuel remains.

A tachometer, by contrast, shows revolutions per minute (engine speed), not total running time. A fuel gauge indicates how much fuel is left in the tank, not how long the engine has run. So the motor’s operating hours are best captured by the engine running time meter.