Why is it necessary to increase dehydration time when using synthetic oil?

Increasing dehydration time when using synthetic oil is necessary due to synthetic oil's higher hydroscopic capability. Hydroscopic materials are those that have the ability to attract and hold water molecules from the environment. Synthetic oils, compared to mineral oils, generally have this characteristic due to their chemical structure which allows them to absorb moisture more readily.

When synthetic oil is used in refrigeration systems, any water that is absorbed can lead to a variety of issues, such as reduced efficiency, corrosion, and potential system failure. Therefore, extending the dehydration time helps ensure that most of the moisture is removed from the system, allowing the synthetic oil to perform optimally without the complications that excess moisture can cause.

The other options may address various aspects of oil performance or characteristics, but they do not directly relate to the necessity of increasing dehydration time in the context given. The focus on hydroscopic capability is pivotal in understanding why managing moisture is crucial when working with synthetic oil in refrigeration applications.