Which four instrument gauges should be checked immediately after starting the engine?

When starting the engine of a tractor-trailer, it's essential to check critical instrument gauges to ensure safe operation. The chosen answer includes the oil gauge, voltmeter, water temperature, and fuel gauge.

The oil gauge is vital because it indicates the oil pressure in the engine, alerting the driver to any potential issues with engine lubrication which could lead to severe damage if not properly monitored. The voltmeter assesses the electrical system's voltage and ensures the battery and alternator are functioning correctly, which is crucial for the vehicle’s electrical components. The water temperature gauge is important for monitoring the engine's cooling system, helping to prevent overheating and potential engine failure. Lastly, the fuel gauge confirms that there is adequate fuel for the journey ahead, preventing the risk of running out on the road.

These gauges provide immediate information about the engine's operational status and overall vehicle readiness, making them essential to check right after starting the engine.