PAG Oil / Polyalkylene Glycol

Table of Contents

Polyalkylene glycol oil or PAG oil is a type of base oil for lubricants. PAG-based lubricants are generally high-quality and longer lasting than other base oil lubricants. Understanding the properties and benefits of PAG oil lubricants can help you make informed decisions when choosing lubricants for your machines.

What are Polyalkylene Glycol and PAG Oil?

Polyalkylene glycol (PAG) is a synthetic substance produced by a process called polymerization. This process combines monomers of ethylene oxide, propylene oxide, and butylene oxide into PAG. 

The PAG-making process was developed 150 years ago with the first PAG polymers used for applications in World War II. Since then, PAG oil has been proven as among the best substitutes for mineral oil as a base for hydraulic fluids, textile lubricants, gear compressors, turbine fluids, etc. 

PAG Oil Properties

Below are the properties of polyalkylene glycol that make it an excellent base oil for lubricants:

High Viscosity Index (VI)

A lubricant’s VI defines its ability to maintain its thickness or viscosity against changes in temperature. A high VI means that PAG oil will have stable performance even with drastic temperature changes.

High Oxidative Stability

High oxidative stability means resistance to oxidation or oil breakdown due to contamination. PAG oil can maintain its performance and lifespan even with exposure to contaminants such as water, solid particles, or high heat.

Low Pour Point

A low pour point means that a lubricant maintains its flow characteristics at very low temperatures. PAG oil does not lose its flow characteristics even at low temperatures.

Solubility in Water

PAG can come in water-soluble forms, making it food-grade and eco-friendly. Most PAG oil products are biodegradable, safe for aquatic life, and do not bioaccumulate in the food chain.

Low Volatility

An oil that has low volatility means it evaporates less when used. PAG oil maintains its low volatility even at high-temperature operations, making it cost-effective to use.

Low Friction Coefficient

Oils with low friction coefficients make them great anti-wear lubricants. PAG oils prevent wear and friction with this natural property.


PAG oil was developed to replace mineral oil lubricants and hydraulic fluids which catch fire more quickly. PAG molecules have lower carbon content than mineral oils and other base oils like esters and polyalphaolefins.

Thermal Conductivity

The molecules in PAG oil conduct heat better than those of mineral oils and other synthetic oils. Thus, PAG oil lubricants provide better cooling on lubricated parts, extending equipment and lubricant life.

Disadvantages of PAG Oils

Because of its properties, PAG oil has a wide range of applications across different industries. But, PAG oil is not without its disadvantages, which include:

PAG Oil is Incompatible with Mineral Oil

PAG oil is not soluble in mineral oil, making it incompatible for use with mineral oil-based lubricants. Replacing mineral oil lubrication with PAG oils requires time-consuming and expensive system change-ups.

PAG Oil Solubility Varies

PAG oils can come in water-soluble, oil-soluble, or intermediate solubility forms. This variation results in variable degrees of lubrication performance, stability, and other properties. The success of using PAG-based lubricants ultimately depends on operation conditions and actual use.

Seal and Paint Incompatibility with PAG Oil Causes Problems

Some chemicals used in seals and paints in equipment or machines can react with PAG-based lubricants. Some PAG oils are not compatible with polyurethane-based elastomers or alkyd-based paints, for example. 

Lubricant Choice Vital to Lubrication Management 

Lubrication is not a one-size-fits-all solution. There is no one perfect lubricant for all machines and operations. You can make informed decisions on the ideal lubricant for your needs, but you still need to confirm its performance. In other words, you can choose the best PAG-based lubricant in theory, but there is no guarantee that this choice fits into your actual operations and processes. 

Effective lubrication management should be a cycle of choosing the best lubricants, confirming their performance, remaking lubricant choices based on the confirmation results, and so on. The performance of lubricants should be monitored, analyzed, and recorded constantly to ensure accurate results and effective lubricant choices and decisions.

If you need accurate and fast lubrication management reporting, you need Lubrication Management Software. With a user-friendly interface, computerized analysis, and cloud-based information, you won’t find a better tool to support inspections confirming lubrication performance. Not convinced? Then, call us for a free demo today!

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