When it comes to industrial air compressors, rotary screw compressors are some of the most widely used and preferred equipment for various applications. Oil-injected and oil-free rotary screw compressors are two of the most common compressor types found in industrial settings. Both types offer exceptional efficiency and performance, but there are significant differences that can make one option more suitable for your specific application.

In this blog post, we explain the difference between oil-injected and oil-free rotary screw compressors in terms of type, application, range, and control. We hope this summarized guide provides a better understanding of rotary screw compressors and how they can benefit your processes.

Types of Rotary Screw Compressors

Before we dive into comparing the two compressor types, let’s explore how a rotary screw compressor works. Essentially, a rotary screw compressor uses two rotors that turn in opposite directions to compress air. As air flows into the compressor, it gets squeezed between the rotors and reduced in volume, resulting in higher pressure. The compressed air then flows out of the compressor and into the air system.

Rotary screw compressors come in two varieties, oil-injected and oil-free. 

Oil-injected rotary screw compressors incorporate oil as a lubricant and coolant for the compression process. The compressed air is mixed with oil and then separated through a filter. This design provides excellent stability, as the oil helps to absorb heat generated during the compression process. This compressor type is ideal for high-demand applications that require continuous operation.

In contrast, oil-free rotary screw compressors use non-contacting, dry screws to compress air. Since there is no friction, there is no need for oil. The lack of oil eliminates the risk of oil contamination in situations where oil contamination is a significant concern. Examples include food and beverage processes, pharmaceuticals, medical facilities, and electronics. 

Applications of Rotary Screw Compressors

Both oil-injected and oil-free rotary screw compressors have their exclusive applications, depending on their oil lubrication requirements. Oil-injected compressors are widely used in various industrial settings, including automotive, construction, manufacturing, and more. They are better suited for environments where oil contamination is not a concern for air quality. 

Oil-free compressors, on the other hand, are preferred for sensitive applications requiring clean air. They are best suited for low to medium applications, such as dental clinics.

Range of Capacity

Another factor that separates oil-injected and oil-free compressors is their capacity range. 

Oil-injected screw compressors usually offer a more extensive capacity range, with choices offering hundreds of horsepower (HP) and pounds per square inch gauge (PSIG). They are ideal for operations with high air demands and extended run times. 

Oil-free screw compressors are limited in their range of capacity. They are more suitable for applications requiring high-quality air, but with limited airflow requirements. These compressors are smaller and more compact, making them a better choice for businesses with limited space.

Controls and Features

Oil-injected and oil-free rotary screw compressors also differ in their control and instrumentation features. 

Oil-injected compressors offer more control options. Control mechanisms for oil-injected compressors involve monitoring and modifying the temperature, pressure, and oil flow required to regulate the compressor’s performance. Multiple air outputs, timers, and automated controls enable users to dial in the right amount of air they need accurately. 

Oil-free compressors possess an advanced control system, thanks to the variable frequency drive (VFD) technology, which adjusts the motor speed to match the air demand. They often feature built-in air dryers and filtration to maintain the air quality and purity its applications require.


The decision of whether to use an oil-injected or oil-free rotary screw compressor ultimately depends on your specific business needs and application. 

If your industrial process requires routine maintenance, lubrication, and cleaning, an oil-injected rotary screw compressor may be the right choice for you. Alternatively, if you need compressed air under sterile conditions or for applications that require contaminant-free air, an oil-free rotary screw compressor would make an ideal choice. 

As experts in providing and servicing industrial pneumatic solutions of premium air compressors, Air Mac will help you choose the right compressor for your business needs. We have a large selection of in-stock and ready to order compressor models to significantly improve your business processes and reduce downtime. Our partnerships with leaders in quality rotary screw compressors, like Sullivan Palatek, Champion, and Kaishan, allow us to provide high-quality compressors you can rely on. 

Contact us today for more information, and our experienced team will guide you through the process of choosing a compressor that successfully meets your goals.