Air compressors can run on a variety of lubricants, but they aren't interchangeable. We've broken down the most common lubricants and how they interact with compressor parts.
A number of oils and lubricants can be used in an air compressor, including polyalphaolefin (PAO) synthetic lubricants, polyoxyalkylene glycol (PAG) synthetic lubricants, polyolester (POE) synthetic lubricants, mineral oil, and diester-based lubricants. Each serves the same basic purpose: ensuring that an air compressor runs as smoothly as possible.
These lubricants aren’t interchangeable, however. Using incompatible lubricants can severely damage the machine. An air compressor designed to run on a PAG lubricant, for example, can be operated with a PAO lubricant, but it is critical to perform a complete flush to remove all traces of the old lubricant before operating on the new lubricant. This may save you some money on the lubricant costs, but may also undermine efficiency and could even damage your air compression system, quickly eliminating any savings you might have gained from the switch.
To help you invest in the right product, we’ve clearly outlined the major differences between the most common lubricants to illustrate how each can benefit (or harm) your air compressor.
PAO lubricants are perhaps the most common lubricant found in air compressors. They’re less prone to oxidation and breaking down, release water well, and have low pour points. They also feature high viscosity, leaving them well-suited to certain applications such as gear and engine lubrication in automobiles.
PAO lubricants have some disadvantages, however. Because of their low inherent solubility, they can’t effectively dissolve additives. Similarly, they cannot suspend degradation-causing byproducts that could damage essential mechanisms in an air compressor. As a result, they carry greater risk when used in air compressors that aren’t designed to handle them.
In some cases, the high viscosity of PAO lubricants can also be a drawback. Since PAO lubricants can increase operating power levels and risk supplying inadequate lubrication to critical points with small diameter flow paths, they should be used in a compressor that runs on a lubricants of a higher ISO level. In addition, PAO degrades rapidly when the operating temperature of the machine increases beyond the normal design point, leaving them ill-equipped for some air compressors.
Like their PAO competitors, PAG lubricants options have high oxidative and thermal stability and a strong VI. According to Machinery Lubrication, they complement these attributes with “excellent film strength and an extremely low tendency to leave deposits on machine surfaces.”
Two classes of PAGs exist. The first type can absorb water, an ability which can keep compressors with condensation or water contamination issues machines well-lubricated. The other is a demulsifier – a product that separates the water from the oil. PAG lubricants dissolve deposits well and burn cleanly, but since they can be somewhat expensive, they may not be the most cost-effective investment if your compressor doesn’t suffer from excessive moisture.
Mineral oil and PAG lubricants share some similar properties, but it’s usually much less expensive, and it offers much greater additive solubility. Since it’s also compatible with many other types of lubricants, it’s easy to combine with other products.
Unfortunately, mineral oil also tends to run hot and break up very quickly, increasing the need for regular oil replacements. As a result, it can cause significant problems in rotary vane air compressors, in which blades hydroplane on a film of lubricant that has one-third of the thickness of a single human hair. If the lubricant breaks down too quickly and the metal blades come into contact with the stator wall, failure will occur.
Diester lubricants enjoy many of the same advantages as other common lubricants, including “excellent oxidative and thermal stability, very high VI and excellent solubility.” They also have strong metal-wetting properties and low volatility. Since they’re also biodegradable, they’re a much more environmentally friendly product. Their high detergency makes them particularly well-suited to air compressors, generating savings that greatly outweigh the initial investment.
The Right Choice
At Mattei, we strongly recommend servicing your air compressor with the lubricant designed for it throughout its working life. Consult your operating manual to determine the right lubricant for your compressor.
We’ve spent decades engineering the highest quality diester lubricants on the market for our rotary vane compressors. Our compressors depend on the outstanding thermal stability and strong solvency of diester lubricants, which don’t break down or adhere to our blades. Because of these properties, they maximize efficiency in every part of our compressors while minimizing the risk of costly mechanical failures. If you’re using a Mattei compressor already or considering working with our products, be sure to ask your distributor about our specialized line of diester lubricants.