If every refrigeration and air conditioning system could always operate at ideal conditions, it is probable the lubricating oils available today would last forever. Thousands of commercial compressors have been operating for 20 years or more without indication of any malfunction. But it is a sad fact of life that much greater numbers of compressors have failed in the last 20 years, some within a few months of installation, due to loss of proper lubrication while operating with that same lubricating oil. Lubrication problems remain the largest single source of failurp on commercial systems, particularly in the low temperature field.

If we were to list the ideal characteristics of a refrigeration oil today, they probably would be outdated by tomorrow, because some cost conscious engineer would try to take advantage of them to extend the compressor operating range a little further. If an oil can withstand 3S0F(177C), we want 375F(l91C); if it can withstand 37SF(191C), we want 400F(204C). If oil will return at -50F(-45C), we want -60F(-51C); if it will return at -60F(-51C), we want -70F(-57C). To a considerable extent many of our problems with lubricating oils are of our own making -- we are constantly pushing at the limits of available technology. If we choose to operate at those limits, then we must accept some percentage of lubrication failures as an inescapeable consequence. Only with a thorough understanding of those limits, and responsible design and operation can we minimize the field problems.