York K oil has a kinematic viscosity of approximately 31.63 cSt at 40°C. This specification is far from arbitrary—if the viscosity is too low, the oil struggles to form a stable lubricating film on bearing surfaces, increasing the risk of wear. If it is too high, oil return efficiency suffers under low-temperature conditions. The viscosity of K oil strikes the optimal balance with the solubility characteristics of R134a refrigerant in the evaporator, ensuring that oil returns to the compressor smoothly along with the refrigerant.
A flash point of 218°C is another critical parameter of York K oil. During high-speed operation, the compression chamber of YK units can approach temperatures near 200°C. If the oil's flash point is insufficient, thermal decomposition and carbon buildup become likely, leading to clogged oil passages or bearing damage. The high flash point of K oil provides ample safety margin under high-temperature operating conditions.
York YK units utilize an ejector oil return system, which relies on high-pressure refrigerant to draw oil from low-pressure areas back to the oil sump. When non-specified oils are used, two common issues arise:
Viscosity deviation: Ejector efficiency declines, oil lingers in the evaporator, and oil levels remain persistently low
Chemical compatibility issues: Reactions with residual oil or sealing materials within the system produce gummy deposits that clog oil return orifices
