FAA Powerplant Written Practice Test

How do turbine engine oils differ from reciprocating engine oils?

1. They are generally thicker

2. They do not require changing

3. They have less tendency to produce lacquer or coke

4. They are more prone to oxidation

The correct answer is: They have less tendency to produce lacquer or coke

Turbine engine oils are specifically formulated to handle the extreme conditions present in turbine engines, including high temperatures and pressures. One of the significant advantages of these oils is their chemical stability, which leads to a reduced tendency to produce lacquer or coke. This stability helps in maintaining engine cleanliness and performance over time, reducing the buildup of harmful deposits that could impair engine operation. In contrast, reciprocating engine oils are designed for different operating conditions and might not possess the same level of resistance to thermal degradation. This difference in chemical composition and characteristics results in turbine oils being better suited for applications where cleanliness and the avoidance of deposit formation are critical. Turbine oils also have unique additive packages that include inhibitors to prevent oxidation and other breakdown products. This characteristic helps to prolong oil life and maintains the integrity of the lubricating film under the high heat generated by turbine operation, contributing to the overall efficiency and reliability of these engines.