Air compressors need oil to reduce friction between moving parts. The right oil helps manage heat and protects internal components. Most manufacturers specify oil types in the back pages of user manuals, often in sections people rarely read.
Compressor oil differs from standard motor oil. A Liverpool engineering firm learned this when they used 10W-30 engine oil in their Atlas Copco GA15. After four months, the compressor developed valve deposits and required a £760 service to fix the problem.
Environmental conditions affect oil choice. A Sheffield metals workshop operating at higher temperatures switched from standard synthetic to PAO-based oil. Their oil temperature dropped by 8°C, extending change intervals from quarterly to twice yearly.
Oil life varies by usage patterns. A Birmingham printing company running their compressor 24/7 changes oil every 10 weeks, while a similar unit used only during day shifts might go 18 weeks between services.
Storage matters, too. Most compressor oils degrade after 12–18 months, even when unused. Labels typically show batch numbers and manufacturing dates in small print on the back of containers.
Below is our guide to air compressor oils.
Types of Air Compressor Oils
Synthetic Oils
Synthetic compressor oils deliver improved performance compared to mineral oils. They are scientifically engineered to offer higher viscosity, reduced oxidation properties, resistance to high-temperature exposure, and better performance under pressure. In certain circumstances, these synthetic oils are suitable for food production environments when the machine is filled with fully-synthetic food grade oil.
Smoother operations through reduced friction result in lower energy costs.
Your air compressor may require synthetic oil because of high peak internal temperatures at certain air pressure levels. Alternatively, the manufacturer may recommend synthetic oils as a performance enhancer. They are also known for extending the length of time between oil changes.
In specific cases, synthetic oils can be used in food production environments when filled with fully synthetic, food-grade oils.
Semi-Synthetic Oils
Semi-synthetic oils strike the balance between synthetic and mineral compressor oils – giving you a little of both worlds.
They have improved viscosity, lower residue deposits, and are not as expensive as synthetic compressor oils. However, you do not get away from all the negatives of mineral oils.
Semi-synthetics are a potential middle ground when aiming to strike a meaningful balance between costlier synthetics and accessible mineral oils.
Mineral Oils
Mineral oil is the earliest type of oil. It is referred to by various names for compressors, including standard compressor oil and mineral oil.
It is more affordable than synthetic or semi-synthetic compressor oil. However, there are trade-offs to consider.
The oil flows less well while achieving reliable thermal consistency, particularly at higher temperatures or humid conditions. It leaves tell-tale deposits and sludge build-up, requiring more regular maintenance shutdowns. Also, the oil must be completely replaced more frequently.
Factors Influencing Oil Choice
It is easy to overlook the importance of compressor oil selection. Nevertheless, no one size fits all.
Every air compressor model operates slightly differently. What is optimal for one model is not always the same for another. Therefore, whilst a previously owned air compressor might have accepted a mineral oil with few inconveniences the same is not automatically true for other compressor makes and models.
Sometimes internal operating temperatures vary between models, or simply due to the settings. For example, temperatures are often higher when requiring higher pressurised air. Your chosen compressor oil must be capable of maintaining its flow rate and reducing friction. Synthetic oils and semi-synthetic oil types are superior at higher internal temperatures.
Also, bear in mind that air compressor manufacturers indicate the type of oil to use. Using a different type of oil than what is recommended may, in a worst-case scenario, void the equipment’s warranty due to potential compatibility issues.
J LL Leach provides advice for compressor owners who are unsure about air compressor oil selection.
Viscosity and Additives
Two aspects of compressor oil to be aware of are viscosity and additives.
Viscosity
Oil flows over the parts to keep them well lubricated and reduce heat build-up. Viscosity refers to a resistance to the necessary flow movement.
UK viscosity ratings confirm an oil product’s level of flow resistance. Lower ratings indicate that the oil flows well in cold conditions but less well in hot ones. Conversely, higher ratings confirm that the oil is well suited to high-temperature internal operating environments.
Look out for oil ISO ratings like the following:
- ISO 32
- ISO 46
- ISO 68
Additives
Oil additives provide useful features that otherwise would not be present.
Additives found more often in synthetic oils include:
Anti-wear: these reduce friction on internal compressor parts for better longevity and less frequent maintenance needs. Clogging is also reduced.
Oxidation inhibitors: these help the oil retain the same chemical and other properties when exposed to air, water, or dust. They maintain optimal performance for longer and extend the oil’s life.
Environmental Considerations
Environmental factors play an increasing role in oil selection. Biodegradable oils are available for environmentally sensitive operations. However, compatibility with your compressor must be confirmed.
Consulting an Atlas Copco specialist ensures an environmentally friendly yet efficient choice tailored to your needs.
More UK environmental regulations complicate the decision. If you are leaning in this direction, we recommend talking with one of our air compressor experts. They can guide you through the various oil choices for your air compressor, allowing you to strike a balance between an environmentally friendly solution and operational efficiency.
Changing and Disposing of Compressor Oil
Air condensate, a mixture of oil and water, is an inevitable byproduct of oil-based compressors. Proper separation and disposal are essential to meet environmental regulations.
The wastewater is then usually compliant with local environmental laws relating to waste disposal. Removing the water through the waste drain is now appropriate. The separated oil must be disposed of safely and in accordance with environmental laws. Fines of upwards of £20,000 are possible when failing to do so.
Common Problems and Solutions
Even well-maintained compressors develop faults. Most issues stem from incorrect oil, poor lubrication or irregular maintenance.
Overheating
Compressors often overheat when running at high pressure or for long periods. Heat breaks down standard oil, reducing protection. Synthetic compressor oil handles higher temperatures better and maintains performance longer.
Foaming and Emulsification
Using motor oil in compressors can cause foaming when air mixes with the oil. Water contamination leads to emulsification, reducing lubrication effectiveness. Always use oil made for your specific compressor model with appropriate additives.
Build-up and Sludge
Standard compressor oil can leave deposits and sludge, particularly in hot workshops. These deposits block valves and passages, reducing efficiency. Semi-synthetic or synthetic oils resist breakdown. Follow the recommended oil change schedule – typically every 500–1000 operating hours for most workshop compressors.
Wear and Friction
Low oil levels or using the wrong viscosity increases component wear. Check oil levels weekly and top up as needed. Most smaller workshop compressors use ISO 100 oil, while larger industrial units often need ISO 150. Your manual will specify the correct type.
Contamination
Workshop dust, moisture from air humidity, and residue from old oil affect lubrication quality. Change filters during oil changes and store your spare oil in a clean, dry cupboard. Many mechanics keep the oil inside rather than in unheated sheds to prevent moisture absorption.
Conclusion
Do not let compressor oil become an afterthought. Selecting a recommended oil protects your capital investment. Choosing poorly can potentially increase expenses during ownership and reduce equipment lifespan.
Choosing high-quality oils with the appropriate viscosity and additives ensures smooth and efficient operation.
If you have questions about air compressor oil, contact our talented team at J LL Leach to help you choose the right one.
FAQ
What type of oil should I use in my air compressor?
The right oil type for your air compressor depends on the make, model, and operating conditions. Always follow the compressor manufacturer’s recommendations. Synthetic air compressor oil is ideal for high-performance and high-temperature environments, while standard air compressor oil may suit smaller or older units. Avoid using motor oil, as it lacks the correct additives and can harm your system.
Can using the wrong oil damage my air compressor?
Yes. Using the wrong oil can lead to overheating, increased friction, and even permanent damage inside the compressor. It can also result in sludge build-up, poor lubrication, or foaming – all of which reduce efficiency and shorten the unit’s life. Always select the right oil for your specific application to protect the compressor.
How often should I change the oil in my air compressor?
Oil change intervals depend on how frequently your compressor is used, the type of compressor, and the oil used. Synthetic oils often allow longer oil change intervals, while mineral oils may require frequent changes. For best results, follow the service schedule in your manual and consider regular oil analysis as part of your air compressor maintenance routine.
