AMP - Aviation Maintenance Technician Powerplant Practice Exam

Propeller manufacturers are the ones who design and manufacture the propellers and know specifically what type of lubricant is required for optimal performance. This makes their instructions the most reliable source when determining oil and grease specifications for lubrication of propellers.

Option A, the lubricant manufacturer's instructions, may not take into account the specific needs of the propellers and could suggest a different type of lubricant that may not be as effective.

Option B, the engine manufacturer's instructions, may provide guidelines for the engine itself, but not necessarily for the propellers.

Option D, the aircraft maintenance manual, may mention lubrication guidelines, but again, it may not be specific to the propellers.

Therefore, option C, the propeller manufacturer's instructions, is the most accurate and relevant choice for determining proper oil and grease specifications for propeller lubrication.