Our Zerol® RFL-EP HP lubricant is a high performance, specially formulated lubricant used in Carbon Dioxide applications. CO2 is one of the main LGWP (Low Global Warming Potential) refrigerants used in heat pump applications. It is low cost, environmentally friendly and effective in producing heat due to the high compression temperatures it requires.  You need an extremely robust lubricant for CO2 applications, making Zerol® RFL-EP HP a superior choice.

A heat pump system uses the same circuit as refrigeration and air conditioning but instead of generating cold air it provides hot air for heating systems in domestic, commercial buildings and industrial applications. Heat pumps obviate the need for a conventional boiler and are more energy efficient and environmentally friendly. Find out more about "what is a heat pump".

With the demand for countries to reduce their impact on global warming and become more environmentally friendly, heat pumps used in domestic, commercial and industrial buildings are becoming more popular in choice over conventional boiler systems for heating and hot water (Find out more about "heat pumps vs conventional boiler systems").  They are more energy efficient and do not require natural fuel resources.  Heat pump technology is the future of hot water and heating systems in building automation.

CO2 is a Low Global Warming Potential natural refrigerant that has a zero ozone depleting impact. Shrieve develops and manufactures lubricants suitable for use with such natural refrigerants.

CO2 is a new refrigerant technology in heat pumps. Within refrigeration applications CO2 has already become a ‘go to’ refrigerant for certain applications, for example supermarket refrigerators, and has been commonly used to replace R134a systems. CO2 provides better system efficiency over R134a refrigerant.  For new build supermarkets CO2 is typically used as a refrigerant choice for its chiller and cold food storage systems.

Can our CO2 refrigerant lubricant be used on other CO2 based systems?

Apart from heat pumps and refrigeration the other applications of our COlubricant include:

  • Automotive - Within air conditioning systems of cars, buses and coaches
  • Transportation of Goods - Within cold food transport refrigeration such as trucks
  • Supermarkets - Cold room storage and food display cabinets

Capped PAG Technology

Zerol® RFL-EP HP is a synthetic polyalkylene glycol (PAG) lubricant technology which employs Double End Capping (DEC) technology, producing a more robust lubricant compared to uncapped, or "Single End Capped" (SEC) PAGs.  A DEC PAG has both ends of the molecule chain capped with an unreactive end group, leaving it chemically inactive.  This makes the molecule chain more robust and improves the lubricating properties of the product, it will not degrade as quickly as uncapped or Single End Capped lubricants.  Further benefits of “capping” can include positive impact on miscibility properties with specific refrigerants, and reduced tendency to adsorb moisture. The RFL-EP HP range has ~95% capping efficiency.


Appropriate miscibility with CO2 over a wide range of lubricant concentration and temperature ranges. This means the lubricant has suitable miscibility with the gas at a variety of temperatures to ensure that it will return to the compressor to maintain lubrication. Despite its good miscibility, the working viscosity of the lubricant is not compromised by CO2 miscibility, compared to alternative lubricant options. Therefore better lubrication is achieved for moving compressor components.


Reduced hygroscopicity compared with water absorbing tendency of uncapped PAGs and POEs. The way in which a water molecule attaches to a DEC PAG is very different to alternative lubricants such as POEs.  Water molecules hydrogen bond onto the RFL-EP HP molecule rather than chemically react with it which means it the lubrication properties of the RFL-EP HP molecule are maintained and the lubricant retains its integrity, compared to other lubricants which are degraded by the presence of water.


High chemical, thermal and hydrolytic stability. CO2 is quite a harsh refrigerant environment therefore the lubricant needs to be robust.  Due to the extreme pressures needed for CO2, you need a lubricant with superior chemical, thermal and hydrolytic stability to avoid breaking down in the system.

ZEROL RFL-EP HP lubricants, based on ‘capped PAG’ technology, provide efficient lubrication for compression type refrigeration units, improved lubricating properties for CO2 systems are achieved as a result of the capping technology. High process efficiency typically results in ~95% capping for the RFL range.

Performance advantages characterising the ZEROL RFL-EP HP range include:

  • Miscibility with CO2 over a wide range of lubricant concentration and temperature
  • Reduced hygroscopicity compared with water absorbing tendency of uncapped PAGs
  • High chemical, thermal and hydrolytic stability
  • Excellent lubricity


Zerol RFL-EP HP Range Typical Properties

Note: Typical properties given do not constitute a supply specification

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