Where can you find the grade of engine oil specified for a particular aircraft?

• A. In the airplane flight manual or the pilot's operating handbook for the aircraft.
• B. In the maintenance manual only.
• C. In the aircraft's registration certificate.
• D. In the fuel system schematic.

Answer: (A)

The recommendation for engine oil is documented in the aircraft’s operating documentation. The airplane flight manual or pilot’s operating handbook lists the approved oil type and viscosity for that specific airframe and engine combination, as specified by the manufacturer. This is the official reference you use when selecting oil. The maintenance manual covers procedures, and the registration certificate or fuel system schematic do not specify the oil grade.