What type of oil was initially used with R-134a automotive systems?

The correct answer highlights that polyalkylene glycol (PAG) oil was initially used with R-134a automotive systems because it provides the necessary lubrication properties compatible with this refrigerant. R-134a, being a hydrofluorocarbon, has different chemical properties compared to older refrigerants that were used with mineral oils. PAG oils are synthesized to work effectively with R-134a systems, providing better lubrication, enhancing system efficiency, and reducing wear on components.

This compatibility is essential for maintaining the performance and longevity of the cooling system. The use of PAG oils specifically caters to the requirements of R-134a, including its solubility characteristics and ability to operate efficiently in the altered refrigerant environment.