Which type of oil should never be mixed in turbine engines?

In turbine engines, it is critical to maintain the integrity and performance of the lubrication system. Mixing different brands or types of oil can compromise the oil's properties and the engine's overall performance. Each brand and type of oil may have unique additives, base oil composition, and performance characteristics that are optimized for specific operating conditions and engine requirements. When these oils are mixed, the resulting blend can lead to chemical reactions that may alter viscosity, reduce film strength, or cause oil degradation. This can result in inadequate lubrication, increased wear, or even catastrophic failure of engine components.

To ensure optimal performance and minimize risks, it is generally recommended to stick with the same brand and type of oil as specified by the engine manufacturer in the maintenance guidelines. This practice helps to ensure that the oil will provide adequate protection under the specific operating conditions of the turbine engine.

The other choices pertain to various properties of oils used in turbine engines, but they do not encompass the critical risks associated with mixing different brands or types, which can lead to severe operational issues.