NOVELTY - Method (M1) for replacing refrigerant in refrigeration system containing chlorofluorocarbon (CFC) or hydrochlorofluorocarbons (HCFC) refrigerant and lubricant, involves: removing refrigerant while leaving substantial portion of lubricant; and adding second different refrigerant (C1) containing fluorocarbon e.g. pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a) or 1,1-difluoroethane (R152a), and hydrocarbon e.g. propane, n-butane or isobutane, and synthetic lubricant; where after replacement synthetic lubricant is (less than 30 wt.%) of total lubricant.    USE - For replacing refrigerant in refrigeration or air conditioning system comprising chlorofluorocarbon (CFC) or hydrochlorofluorocarbons (HCFC) and lubricant (claimed). The refrigeration systems further include e.g. chillers (e.g. centrifugal chillers, screw chillers, direct expansion chiller, or flooded evaporator chiller), heat pumps, transport refrigeration systems, and commercial refrigeration systems such as supermarket racks or single condensing units.    ADVANTAGE - The method provides improved method for replacing refrigerant in a refrigeration or air conditioning system containing chlorofluorocarbon (CFC) or hydrochlorofluorocarbons (HCFC) refrigerant and hydrocarbon lubricant, with refrigerant composition comprising fluorocarbon and hydrocarbon without flushing to remove residual lubricant by introducing synthetic lubricant to such systems, where resultant lubricant composition has relatively low solvency power. Historically, retrofits of systems using hydrofluorocarbon refrigerants and mixture of polyol esters (POE) and mineral oil required multiple oil flushes with POE to remove residual mineral oil. This procedure had benefit of cleaning system because dissolved contaminants were removed with POE during flushing. However, partial POE retrofit procedures entail removing significant portion of mineral oil and replacing it with POE without performing any flushes. This partial POE retrofit procedure introduces significant amounts of POE into system (30-90%) without any flushing or POE removal. Contaminants dissolved by solvency power of oil mixtures with high levels of POE can redeposit and cause system plugging and other detrimental effects. It is found that certain refrigerants, such as ISCEON (RTM: hydrofluorocarbon refrigerants) require no addition of POE in most cases. This is because ISCEON refrigerants contain a small amount of hydrocarbon refrigerant which improves solubility with mineral oil. For some difficult oil return systems where mineral oil solubility is not sufficient to provide adequate oil return a small amount of POE is recommended (5-20%), and it has been learned that this does not significantly impact the solvency power of mineral oil/POE mixture. It is found that even in presence of refrigerant with lubricant, mixtures with lower amounts of POE have lower Kauri-butanol values. Adding lower amounts of POE (less than 30 wt.%) aids oil return, but reduces potential to dissolve and redeposit contaminants in system which can result in system performance issues. In the composition (C1) and (C1a), the combination of hydrocarbon-based lubricant and synthetic lubricant resulting after refrigerant replacement has a Kauri-butanol value of less than 35 (where higher Kauri-butanol value means solvent is more aggressive or active in ability to dissolve certain materials, and mild solvents have low scores of Kauri-butanol value), and an aniline point temperature of at least 60 degrees C (where lower aniline point is indicative of stronger solvency power). Thus the method effectively reduces amount of POE used to lubricate hydrofluorocarbon refrigerant compositions; and provides an option for refrigeration industry of providing hydrofluorocarbon refrigerant as replacement refrigerant for ozone depleting CFCs and HCFCs.    DETAILED DESCRIPTION - Method (M1) for replacing a refrigerant in a refrigeration or air conditioning system containing a first refrigerant comprising a chlorofluorocarbon (CFC) or hydrochlorofluorocarbons (HCFC) and a first lubricant, involves: removing the first refrigerant from the refrigeration system while leaving a substantial portion of the first lubricant in the system; and adding a second refrigerant or a replacement refrigerant (C1) different from the first refrigerant and comprising a fluorocarbon selected from pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), difluoromethane (R32), 1,1-difluoroethane (R152a), 1,1,1-trifluoroethane (R143a) and/or octafluoropropane (R218), and a hydrocarbon selected from propane, n-butane, isobutane, n-pentane, isopentane, and/or dimethyl ether; and a synthetic lubricant component; where after refrigerant replacement the synthetic lubricant component is (less than 30 wt.%) of the total amount of lubricant in the system. An INDEPENDENT CLAIM is included for a composition (C1a) comprising: a refrigerant comprising a fluorocarbon selected from R125, R134a, R32, R152a, R143a and/or R218, and a hydrocarbon selected from propane, n-butane, isobutane, n-pentane, isopentane, and/or dimethyl ether; and a lubricant comprising a hydrocarbon-based lubricant component, and a synthetic lubricant component (less than 30 wt.% of the lubricant).