Which of the following items is specifically required as part of Day VFR equipment?

The requirement for an oil temperature gauge as part of Day VFR (Visual Flight Rules) equipment is grounded in safety and operational standards for aircraft. Under aviation regulations, it is essential for pilots to have instruments that monitor the aircraft’s engine performance. An oil temperature gauge provides critical information about the operating temperature of the engine oil, allowing pilots to ensure that the engine is functioning within safe parameters. Overheating can lead to engine failure, so having real-time monitoring ensures that the pilot can respond to any anomalies effectively.

In contrast, while the other items listed may be valuable for various operations or aircraft types, they are not mandated for Day VFR operations. Weather radar, while useful for navigating around storms, is not a requirement for visual flying during the day. A flight data recorder is primarily used for accident investigation and is not necessary for normal flight operations. An autopilot system, while beneficial for reducing pilot workload, is also not a regulatory requirement for flying under Day VFR conditions. Therefore, the oil temperature gauge stands out as a specifically required instrument for ensuring safe and effective operation of the aircraft during daytime VFR flights.