Quite the contrary. So long as the container of POE is tightly capped after each use, the oil can be used until the container is exhausted.
All of the refrigerants that are recommended as "CFC replacements with no oil change" are blends that incorporate a significant level of R-22 as part of the gas. And because R-22 has marginal miscibility with mineral oil, use of the "no oil change" approach will jeopardize system performance, particularly in low temperature application. Change the oil to an alkylbenzene like Zerol. Use of mineral oil with these refrigerants encourages problems like carbonization or burning of the mineral oil, loss of capacity, loss of efficiency, etc.
Answer: The best service tool is a refrigeration oil acid test kit, and the best acid test kit technology is one that incorporates a "phase separator" in the test procedure like our Phase III Test Kit. The phase separator separates the oil being tested from its acid content, and that permits easy, accurate determination. In fact, the Phase III Test Kit can be used on all three oils: mineral oils, alkylbenzene oils, and polyol ester oils (both ICI and Mobil).
Miscibility is the ability of two substances to mix together. When using the term in discussing refrigerants and oils, it refers to the ability of the gas and the oil to remain as one mixture, one homogeneous mixture, as they travel through the system, from the compressor and back to the compressor. Proper heat transfer and efficient system operation require an oil and a gas that exhibit good miscibility, particularly in the evaporator where temperatures are lower. Polyol esters (POE’s) have good miscibility with all refrigerants while alkylbenzenes like Zerol have good miscibility with both CFC’s and HCFC’s: (especially HCFC’s because of their R-22 content). Mineral oils exhibit the best miscibility with R-12, and only marginal miscibility with R-502 and HCFC’s.
Without question, you should use an alkylbenzene lubricant like Zerol, and for one very good reason: Zerol alkylbenzene has the best miscibility with R-22, significantly better than mineral oil, and it’s use with R-22 will insure good oil return to the compressor and no oil logging in the evaporator.
Because of the mineral oil’s poor miscibility with the targeted HFC. Use of HFC’s requires the use of a POE oil and optimum system performance will only be achieved when the mineral oil content is below 3-5%.
Because the HFC’s have very poor miscibility with mineral oil and only marginal miscibility with alkylbenzenes. HFC’s exhibit excellent miscibility with POE’s.