FAA Powerplant Written Practice Test

After the break-in period of a new reciprocating engine, which type of oil is most often recommended?

1. Ashless-dispersant oil

2. Conventional mineral oil

3. Semi-synthetic oil

4. High-mileage oil

The correct answer is: Ashless-dispersant oil

The most often recommended type of oil after the break-in period of a new reciprocating engine is ashless-dispersant oil. This type of oil is specifically designed for use in aircraft engines and provides several advantages that are crucial for maintaining engine performance. Ashless-dispersant oils are formulated to keep engine parts clean by suspending contaminants and preventing deposits from forming. This is particularly important after the break-in period when the engine components have been seating and wearing in, potentially releasing metal particles and other contaminants into the oil. The dispersant properties help to manage these particles, preventing them from settling on critical engine components and allowing for continued lubrication and cooling. Furthermore, these oils provide adequate protection against wear, oxidation, and breakdown at the high temperatures and pressures found in airplane engines. They are specifically tested and certified to meet aviation standards, ensuring that they will operate effectively in the demanding environment of an aircraft engine. The other types of oils mentioned, while useful in certain situations, do not offer the same combination of cleanliness and protection as ashless-dispersant oils, making them less suitable for use in aircraft engines after the break-in period.