PLZ help me. Why does CPI 1507-68 (PAG) color in screw compressor (MYCOM G250 LUD-H) change to D8 after 540 hrs operation.
This compressor is used for butane vapore liquefying. Properties of oil do not change ( viscosity @ 40 & 100, TAN, FP, ....).
Carbon residue for new oil is 0.5% and for used oil is 1.5%. Any experience.