Which of the following is true about hygroscopic oils?

Hygroscopic oils are characterized by their ability to absorb moisture from their surroundings. This property is significant because when hygroscopic oils are used in refrigeration systems, they can draw moisture into the oil, which can lead to the formation of acids and sludge when water reacts with refrigerants. This condition can cause detrimental effects on system components and reduce the efficiency and longevity of the equipment.

Understanding the nature of hygroscopic substances is crucial for technicians working with refrigeration systems, as managing moisture levels is vital for maintaining system integrity. The term "hygroscopic" itself specifically denotes a substance's tendency to attract and hold water vapor, which is why this option accurately describes the properties of hygroscopic oils.

Other choices suggest incorrect characteristics of hygroscopic oils, such as repelling moisture or being non-moisture absorbent, which do not align with the definition and behavior of hygroscopic substances. Additionally, the suggestion that these oils evaporate when moist does not relate to their fundamental property of moisture absorption. Understanding these key concepts is essential for effective troubleshooting and maintenance in HVAC systems.