Which Air Compressor: Oil-lubricated or Oil-free?

Wondering what the difference is between oil-lubricated piston compressors and oil-free reciprocating compressors? Or which one fits your business? Find out more in this blog!

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Estimated time to read: 3 minutes

September 12, 2022

Oil-lubricated Piston Compressor or Oil-free Reciprocating Compressor?

In our previous Know Your Air blog post, we discussed how a piston compressor works. This time, we look at the difference between oil-lubricated and oil-free piston compressors. Which one is best for your needs? 

Why lubricate?

Whether it’s a screw compressor, centrifugal compressor or piston compressor, (also known as a reciprocating compressor), every mechanical air compressor has moving parts. And whenever a moving part, such as a piston, presses against a non-moving part, such as a piston sleeve, the softer material will inevitably suffer wear and tear. With lubrication, you reduce the amount of contact the parts have. In doing so, you reduce the friction, and of course, the wear and tear. 

Oil-lubricated piston compressors

In an oil-lubricated piston compressor, the cylinders, pistons and cranks are lubricated with oil that circulates throughout the compressor. As a result, residual oil ends up in the compressed air produced by your oil-lubricated piston compressor. It's a tiny amount, typically around 10–15 mg/m³. In most cases, it’s nothing to worry about. However, there are situations in which you need to avoid it.

Oil-free reciprocating compressors

The food-and-beverage, electronics and medical industries all require compressed air that is completely free from oil. The solution? An oil-free reciprocating compressor. Most oil-free reciprocating compressors have permanently lubricated bearings. The pistons use grease-free piston rings that are usually made from carbon fiber or coated in Teflon. An oil-free reciprocating compressor usually needs to have its bearings and piston rings replaced more frequently than an oil-lubricated compressor. 

Oil-lubricated vs oil-free reciprocating compressors

A lot of oil-free reciprocating compressors have fewer moving parts than you’ll find in oil-lubricated compressors. This means they often weigh less and come with a smaller price tag. In the past, they were also considered to be noisier, although this isn’t necessarily the case nowadays. In many cases, oil-free reciprocating compressors are less powerful than their oil-lubricated cousins.

Want to know more about keeping your compressed air free from oil and other unwanted particles? Read our blog post on compressed air filters.