Refrigeration Oil Isn't Just "Any Oil" — Matching Oil to Refrigerant
Put the wrong oil in a compressor and you will ruin it. Here is how oil and refrigerant have to match in the field.
In the last note I showed a compressor with oil burnt jet-black. So what should normal oil — and the right refrigerant — actually be? This is about the two things that keep a compressor alive: refrigeration oil and refrigerant.
Refrigeration oil does three jobs, not one: lubrication (bearings, pistons, crankshaft), cooling (it carries away some internal heat), and sealing (it fills the tiny gap between piston ring and cylinder so compression does not leak back). When the oil runs low or burns, all three fail at once — and the compressor dies.
The key point: the oil depends on the refrigerant. R-22 and other HCFCs use mineral oil (like the SUNISO 3GS shown). R-410A, R-404A and other HFCs need POE (polyol-ester) synthetic oil — mineral oil will not mix with them and lubrication breaks. Put R-22 mineral oil into an R-410A system and even a healthy compressor seizes its bearings before long. "It is oil, so anything goes" is exactly the mistake to avoid.
R-22 itself is being phased down worldwide (it is an ozone-depleting HCFC), so you will meet R-410A, R-404A and R-32 more and more — and each wants its own oil. Three field rules: match the oil to the system's refrigerant on every compressor change or overhaul; never mix refrigerants in one system; top up oil with the same spec. Because every site runs a different refrigerant, I note the refrigerant and oil type per customer and unit in R-Pro — next visit, no guessing.