Polyolester oil (POE oil) is a type of synthetic oil used in refrigeration compressors that is compatible with the refrigerants R-134a, R-410A, and R-12. HFC-134a with POE oil as the lubricant is a replacement for CFC-12 with mineral oil as the lubricant as HFC-134a does not mix well with mineral oil. These wax-free oils are suggested for use with chlorine-free HFC systems as they provide better lubrication and stability and are more miscible with HFC refrigerants. They can match the lubricity properties of mineral oils used with CFCs and HFCs. They are compatible with most lubricants in the market. The viscosity of the oil decreases with temperature. The dispersion behavior of this oil has been heavily studied. It is also considered by some to be a good additive to engine oil.
Problems
The same properties that make POE oil a solvent for oils also make it a solvent for other pieces of matter left behind during the manufacturing of a unit, such as dust, dirt, residue from soldering, small metal bits, and oxidized metal from the tubing. The residues collected can clog the system filters and cause excessive wear or damage to components such as the vanes or valves. Therefore, the components must be machined, deburred, and cleaned. These oils are also hygroscopic in nature and thus can absorb moisture from the atmosphere.
POE oils typically have lower viscosity indexes than polyalkylene glycol (PAG) or poly-alpha-olefin (poly-α-olefin, PAO) oils so that a higher viscosity grade is required in order to attain a certain kinematic viscosity at higher oil temperatures.