The change-over from R-12 to one of the new blends has proven to be a rather simple procedure involving only the changing of the lubricant and the filter/drier. In a few cases , the expansion valve and /or other controls require minor adjustments. With R-401a and R-401b the compressor suction pressure with R-12 for most medium temperature applications. Compressor discharge pressures are usually 10-20 psi (70-140 kPa) higher than with R-12.