Air compressors are a punishing application for any lubricant. The lubricant is subjected to high temperatures, contaminants and often harsh environmental conditions. Air compressor lubricants need to handle these tough conditions, while providing the following critical functions.
Protect against wear and friction
Like any lubricant a air compressor oil protects against wear and friction by separating moving surfaces which helps prevent metal on metal contact. This separation layer is incredibly thin often less than 4µm (less than the thickness of a human hair).
A critical factor in maintaining this separation is the viscosity of the oil. If the viscosity of the oil is too thin the lubricant will not be able separate the moving surfaces. If the lubricant is too thick, then increased friction and heat will result. The correct viscosity of a lubricant is typically selected by the manufacturer of the compressor.
| Compressor Type | Typical Viscosities |
| Rotary Screw | 32, 46, 68 |
| Piston (Reciprocating) | 68, 100, 150 |
| Rotary Vane | 100, 150 |
| Centrifugal | 22, 32 |
| Rotary Lobe Blowers | 150, 220 |
Since compressors in high temperature environments often operate at higher temperatures, it is typically suggested to use a higher viscosity oil. This is because the viscosity of the oil decreases as the temperature rises.
Sealing
Air compressor lubricants can also increase compression efficiency by creating a seal. In a rotary screw compressor, the oil creates a seal between the rotating male and female rotors.
Heat Transfer
An air compressor lubricant also must transfer heat. A lubricant with poor heat transfer properties can lead to excessive temperatures which can lead to catastrophic equipment failure due to thermal expansion.
Fluid Life
The combination of air and high temperatures leads to the mortal enemy of any lubricant, oxidation. When an oil oxidizes it increases in viscosity and acidity. This higher viscosity increases friction which results in increased temperature. In addition, oxidized oil produces sludge and varnish. These deposits can become trapped in the oil cooler, which reduces its effectiveness, leading to further increases in temperatures.
This becomes a vicious cycle since the higher the temperature the faster the rate of oxidation. This is why selecting an oil with a long oil life not only allows for extended drain intervals but improves operational efficiency.
As a general rule for every 10 °C, the life span of an oil is reduced by half. As most air compressor lubricants oil life’s are set at 90 °C they will be unlikely to provide their claimed oil life since at todays higher operating conditions their lifespan will likely be cut in half.
Next Lubricants are designed to provide superior resistance against oxidation. The hour life of all Next Lubricant air compressor oils are set at 100 °C this helps ensure that our oils will meet expectations.
In addition, Next Lubricant air compressor oils have been specially formulated to resist oxidation. Formulations like Aero XL are formulated to provide a fluid life of between 8.000 to 12.000 hours. Next Lubricants air compressor oils are also much less likely to form sludge especially when compared to competitive formulations.
