R-134a Systems

CAUTION: Do not add R-134a refrigerant oil to an R-12 system. Also, do not add R-12 refrigerant oil YN-9 to an R-134a system. Mixing these two types of refrigerant oils may cause poor lubricant circulation resulting in component failure and damage to the A/C systems.

The refrigerant oil required for R-134a A/C systems is a polyalkylene glycol (PAG) oil Ford part number F2AZ-19577-AB (Motorcraft YN-12b) or equivalent meeting Ford specification WSH-M1C231-B. This type of refrigerant oil was made specifically for R-134a systems and is not suitable for use in R-12 systems. Never use an R-134a refrigerant oil in R-12 systems.