FAA Powerplant Written Practice Test

Which of the following is NOT a function performed by engine oil?

1. Cool the engine

2. Prevent corrosion

3. Act as a fuel substitute

4. Clean internal components

The correct answer is: Act as a fuel substitute

Engine oil serves several vital functions in an aircraft engine, including cooling, preventing corrosion, and cleaning internal components. It plays a critical role in maintaining optimal engine performance and longevity. When we consider the tasks that engine oil performs, cooling is achieved by absorbing heat from engine components and transporting it away, thereby helping to maintain proper operating temperatures. The oil also contains additives that help prevent corrosion by forming a protective barrier on metal surfaces, which is crucial in preventing oxidation and wear. Additionally, engine oil acts as a detergent, helping to clean internal components by suspending contaminants and preventing sludge accumulation. However, engine oil does not act as a fuel substitute. While it is essential for lubrication and supporting various engine functions, it is distinct from fuel, which is necessary for combustion and energy production within the engine. Fuel substitutes serve a different purpose, mainly providing the necessary energy required for engine operation, which is unrelated to the lubrication and protective functions of engine oil. Thus, identifying that engine oil does not replace fuel clarifies its specific role in the engine's overall operation.