Which type of oil has the highest ability to absorb moisture?

PAG oil, or polyalkylene glycol oil, is recognized for its high hygroscopic nature, meaning it has a strong capacity to absorb moisture from the environment. This characteristic is particularly important in refrigeration applications, where moisture can lead to several issues, including reduced efficiency, corrosion, and the formation of acids within the system. PAG oils are often used in applications involving refrigeration and air conditioning systems, especially those utilizing refrigerants like HFCs.

In contrast, mineral oil has a lower ability to absorb moisture, making it less effective in environments where humidity is a concern. Esters, while they do have some moisture-absorbing properties, do not possess the same level of hygroscopicity as PAG oils. Propylene glycol, commonly used as an antifreeze, also has moisture absorption characteristics, but its primary use is quite different from that of oils intended for refrigeration systems.

Thus, PAG oil's ability to intake and interact with moisture is critical in maintaining the integrity and functionality of refrigeration systems, while the other types of oils are not tailored for this purpose in the same way.