Since it is not compatible with mineral oils, it should be used with polyolester or polyolalkaling glycol based oils. R404a is a near azeotropic mixture of R32 and R125 (50/50% by weight) which is considered an alternative to R22. Its theoretical thermodynamic properties are not as good as R22. However, its heat transfer property is quite good. In R22 – R410A conversion, the system needs to be redesigned.