Final answer:
POE (Polyolester) oil is the synthetic oil commonly used with HFC refrigerants due to its compatibility and stability. PAG oils are generally used in automotive systems with R-134a and are not suitable for most stationary HFC systems.
Step-by-step explanation:
The synthetic oil commonly used with HFC refrigerants is POE (Polyolester) oil. POE oils are compatible with the newer HFC refrigerants. They are hydrolysis stable and have good lubricity and thermal stability, making them suitable for high-temperature applications. Unlike mineral oils and alkyl benzene oils (AB), which were commonly used with older CFC and HCFC refrigerants, POE oils do not have issues with moisture, which can be critical with HFC systems. PAG (Polyalkylene Glycol) oils are typically used in automotive air conditioning systems with R-134a and are not recommended for use with most HFC refrigerants in stationary systems.