With a broad choice of air compressors, one of the deciding factors in selecting the right tool for the job can relate to the type of lubrication used – or whether you are better off with an oil-free non-lubricated compressor.

Compression lubrication types matter


Because when you’re working with compressed gas systems, it’s essential the compressor keeps running.

Air compressor lubrication types are responsible for cooling, sealing and lubricating the internal components. Inadequate lubrication means that your equipment is vulnerable to breakdowns and knock-on downtime, and repair costs.

Here we’ll explain why it’s vital to choose the correct compressor lubrication types and the primary options available!

How Important is My Choice of Compressor Lubrication Types?

One of the first points to make is that the suitable compressor lubrication types depend on:

  • The kind of air compressor you have.
  • The environment it is used in.
  • Which gas is being compressed (we’re exploring air compressors here, but it’s worth noting that compressors can be used for other applications).

Great compressor lubrication types provide high-performance specifications that protect against rust, restrict corrosion, are non-foaming, have demulsibility properties (they shed water) and have high oxidation stability.

Compressor lubrication types are suited to a particular type of compressor whether that’s a rotary vane, dry screw, centrifugal or reciprocating compressor.

Different Compressors and Compressor Lubrication Types

OK, so let’s crack on with explaining the different options and their compressor lubrication types!

Oil Lubricated Air Compressors

We’ll start with a standard lubricated air compressor, widely used in industrial applications and manufacturing. These compressors inject oil directly into the compression chamber, lubricating the internal moving components.

Piston Compressors

Next up, a piston compressor uses one of two methods to lubricate the running gear, rings and cylinder walls:

  • Splash lubrication means a dipper rod at the bottom of the piston rod. This rod dips into the oil and splashes it from the sump onto the pistons and running gear – hence the name!
  • Less commonly, you can find pressure lubrication with an oil pump moving oil through drilled pathways in the compressor. These compressors use a filter to remove any contaminants from the oil that is then recirculated.

Rotary Compressors

A rotary compressor also uses a pressure system to pump oil into the lubrication system, pulling it from the sump.

Oil passes through the cooler before reaching the compressor pump to reduce the temperature. Again, you’ll find an oil filter to remove any impurities.

After filtering, the oil is injected into the air-end, lubricating any gears and the bearings, sealing rotors and maintaining stable temperatures.

Following this process, the oil travels through an air-oil separator, separating oil from air and storing it back in the sump.

Centrifugal Compressors

We’ll explain oil-free compressor lubrication types in a second. Still, centrifugal compressors are a device that falls into this category since they don’t allow oil to enter the compression chamber.

While parts of the compressor are still lubricated, they are kept separate with air and oil seals, using a vent area.

What Compressor Lubrication Types Are Used in Oil Free Compressors?

So, for this guide, we’ll assume that oil-free compressors are ISO Class-0 rated – i.e. they have a 100% oil-free specification, and no oil can come into contact with compressed air.

Other compressors are technically oil-free and have minimal oil contaminants, so they retain a high level of air purity but without zero oil levels in the vapour.

Oil-free compressors are the gold standard of compression, used in many delicate manufacturing processes, such as producing semiconductors or making pharmaceutical products.

Every compressor still requires lubrication, so there is still oil found in the equipment. However, an oil-free reciprocating compressor or an oil-free rotary compressor will lubricate the components and seal the rotors without contaminating the air.

They incorporate specialist sealants such as Teflon piston rings or coated rotors. In addition, they have properties like water sealing and timing gears to separate rotors and ensure the lubrication process cannot reach the compression chamber.

Why is it Essential to Choose the Right Compressor Lubrication Types?

As we’ve discovered, lubrication is key to an air compressor’s functions, so opting for the best quality lubrication is essential to keep your equipment running correctly and operating precisely.

Commercial air compressor lubricants provide a range of benefits, such as:

  • Protection from wear, rust and corrosion.
  • Filterable properties to keep the oil clean.
  • Thermal stability for long-term heat control.
  • Resistance to heat, moisture and oxidation.
  • Eliminating sludge and deposits.
  • Antifoaming performance.

Remember, the compressor lubrication types available will depend on the air compressor you use, and so it’s vital to choose appropriate lubrication to keep your equipment running in perfect condition.