07/05/2026 by Thomas Clark
Industrial lubricants are critical components for refrigeration systems that run on CO2 refrigerant.
Refrigeration compressor oil is designed to lubricate moving parts effectively to ensure they can perform properly while promoting compression by creating a strong seal.
During low circulation speeds, oil can build up in components and become deposited on the walls of evaporators and other heat exchangers, reducing efficiency. The oil must return to the compressor, or the oil pump can prime itself and seize the system. As a result, it is vital that the compressor oil selected for an application is miscible with CO2 in its liquid state and soluble with its gaseous state, with the ability to handle operating temperatures and pressures.
Here, we look at the lubricants that work correctly in CO2 refrigeration systems and explore some important considerations for CO2 lubrication. We’ll also look at some leading lubricant brands that are recommended for optimal refrigeration operations when CO2 is the refrigerant.
Top lubricant types recommended for CO2 applications
A range of lubricants are available that have characteristics which match CO2 refrigeration systems. These include Polyalkylene glycol (PAG), polyolester (POE) and some specialised oils.
Polyalkylene glycol (PAG) oils
PAG oils are an ideal choice for refrigeration systems because of their exceptional miscibility with CO2. Their other key benefits include providing good lubricity when working under high pressures and having both high thermal and chemical stability.
PAG oils are known for maintaining sufficient viscosity to protect refrigeration compressors and for preventing wax formation. Lubricant experts agree that in certain applications, PAG oils provide superior lubrication to other options, like POE oils. PAG oils see frequent use in heat pumps and mobile air conditioning systems.
Polyolester (POE) oils
POE oils are often selected for CO2 refrigeration because of their excellent miscibility with the refrigerant. This capacity to effectively mix with CO2 lets oil effectively return to the refrigeration compressor and promotes proper lubrication.
POE oils can withstand high pressures and have high thermal stability. They can also inhibit varnish formation and offer good protection against friction and wear. POE oils are a favoured solution for industrial refrigeration.
Specialised oils
Specific lubricants like the POE oils Emkarate RL68H (also known as Copeland RL68) and Bitzer BSC 85K are often matched to compressors. The former is suitable for some CO2 applications, while the latter is engineered specifically for high performance CO2 systems.
Key points to consider regarding CO2 lubrication
Compared to other refrigerants, CO2 operations involve higher temperatures and service pressures that create extreme mechanical stress on bearings and moving parts. Added to oil, CO2 is extremely soluble, causing lubricants to lose their viscosity and, in some cases, cause protective oil films to break down.
Consequently, when an incorrect oil is deployed, insufficient lubrication can occur, causing premature system wear, seal faults and reduced compression.
PAG and POE oils offer superior high-pressure stability over standard mineral oils, ensuring they can adequately lubricate components and provide a strong seal. It is worth noting, however, that both PAG and POE oils are hygroscopic. They absorb moisture like a sponge, which can form acid and sludge in systems. As a result, extreme care is required during handling. Best practices involve ensuring minimal exposure by keeping containers sealed until the precise moment of use.
When selecting a lubricant for a CO2 refrigeration application, the best option is a high-quality, wax-free synthetic oil that can promote system efficiency and prevent any damage to the compressor.
Recommended lubricant manufacturers
Today, leading lubricant manufacturers like CPI Fluid Engineering formulate advanced refrigeration compressor oils that are specifically designed to work with systems where CO2 is the refrigerant. These cutting-edge solutions are engineered to effectively answer operational challenges in applications involving high pressures and solubility. These include products in the Icematic Eco Series and the synthetic lubricant CPI-4624-F, which are developed and optimised for use with CO2 refrigeration applications, especially for rotary compressors.
Their key properties that make them suited to CO2 systems include excellent chemical stability so they can resist varnish formation and thermal degradation, optimised viscosity to ensure correct sealing and lubrication in high-pressure environments and improved oil return to the compressor due to their excellent miscibility with carbon dioxide.
You may also interested in:
How to choose a reliable industrial lubricant supplier
Operations involving mechanical equipment require lubricants to run effectively.
Why do lubricant prices change?
From Texaco and TYGRIS to Shell and Solest, there are a wide range of lubricant brands providing products for global distribution.