6 Common Causes of High Oil Consumption in Screw Air Compressors and How to Fix Them

In industrial production, screw air compressors are widely used because of their stable air output, high efficiency, and relatively low maintenance cost. They are a key part of compressed air systems in factories.
However, high oil consumption is one of the most common faults during operation. This problem not only increases lubricant cost, but also contaminates compressed air, blocks downstream filters, and may even damage pneumatic equipment.

Based on real on-site maintenance experience, this article explains the main causes of excessive oil consumption in screw air compressors and provides clear, step-by-step troubleshooting methods. The language is simple and practical, making it easy for technicians to understand and apply. This guide is also optimized for SEO, helping users quickly find useful solutions.

1. Check the Oil-Air Separator First

The oil-air separator is the most important part for controlling oil content in compressed air. If it fails, oil consumption will increase sharply.

1.1 Service Life of the Oil-Air Separator

• Most manufacturers recommend replacing the oil-air separator after 2000–3000 operating hours.

• If it is used for too long, the separator element may become clogged or damaged.

• Once the separation effect is lost, large amounts of oil will enter the air system.

What to do:

• Check the running hours of the separator.

• Replace it if it has exceeded its service life.

1.2 Physical Damage to the Separator Element

After shutdown and pressure release:

• Remove the separator element.

• Check the surface carefully.

Common problems include:

• Tears or holes in the filter material

• Excessive oil accumulation at the bottom

Solution:
If any damage is found, replace the separator immediately.

1.3 Poor Sealing of the Separator

If the sealing gaskets on the upper or lower flanges are aged or deformed:

• Oil and air may bypass the separator.

• This causes oil loss and gives the impression of high oil consumption.

Solution:
Check all seals and replace old or damaged gaskets.

2. Check Oil Tank Pressure and Oil Level

The oil tank (oil-air vessel) plays a key role in oil circulation and separation.

2.1 Oil Tank Pressure Problems

• If pressure is too high, oil mist cannot settle properly.

• If pressure is too low, oil flows too fast and does not have enough time to separate.

Both situations can increase oil carryover.

Solution:
Ensure the oil tank pressure stays within the rated range specified by the manufacturer.

2.2 Incorrect Oil Level

Oil level is often ignored, but it has a big impact.

• Oil level too high:
  Oil can be directly carried out with compressed air.

• Oil level too low:
  The compressor may overheat, which can also increase oil consumption.

Correct method:

• Stop the compressor.

• Release internal pressure.

• Check the oil level through the sight glass.

• Make sure it is between the minimum and maximum marks.

3. Inspect the Temperature Control Valve and Cooling System

The temperature control valve controls whether oil flows through the cooler. Its condition directly affects oil temperature.

3.1 Temperature Control Valve Failure

If the valve is stuck in the closed position:

• Oil cannot enter the cooler.

• Oil temperature will continue to rise.

High oil temperature causes:

• Lower oil viscosity

• More oil mist

• Poor separation efficiency

Normal oil temperature:
75°C to 95°C

Solution:

• Check the oil temperature during operation.

• If temperature is too high, remove and clean the temperature control valve.

• Replace the valve if it is damaged.

3.2 Oil Cooler Blockage

If the cooler is dirty or blocked:

• Heat cannot be released effectively.

• Oil temperature stays too high.

Solution:

• Clean the oil cooler regularly.

• Ensure cooling air or water passages are clear.

4. Check the Oil Return Line and Check Valve

After separation, oil must return to the air end through the oil return line.

4.1 Blocked Oil Return Line

If the oil return line is:

• Bent

• Blocked by dirt

• Internally clogged

Then separated oil cannot return and will be carried out with compressed air.

Inspection method:

• Stop the compressor.

• Remove the oil return line.

• Blow air through it to check for blockage.

4.2 Faulty Check Valve

The check valve ensures oil flows in one direction only.

If it is:

• Stuck

• Worn

• Not sealing properly

Oil cannot return smoothly.

Solution:

• Check the movement of the check valve.

• Replace it if it does not open or close smoothly.

5. Check the Air End and Internal Wear

If all external parts are normal, the problem may come from the air end itself.

5.1 Bearing Wear and Shaft Seal Failure

Inside the screw air end:

• Worn bearings

• Aged shaft seals

These problems allow oil to enter the compression chamber directly and exit with the air.

5.2 Rotor Clearance Problems

If rotor clearance becomes too large:

• Compression efficiency drops

• Oil temperature rises

• Oil consumption increases indirectly

Signs of internal problems:

• Abnormal noise

• Increased vibration

• Higher operating temperature

Solution:

• Measure vibration and noise levels.

• Stop the compressor if abnormal values are found.

• Inspect bearings, seals, and rotor clearance.

• Perform overhaul if necessary.

6. Follow the Right Troubleshooting Order

When dealing with high oil consumption in screw air compressors, always follow this rule:

From simple to complex, from outside to inside

Recommended order:

1. Oil-air separator

2. Oil level and oil tank pressure

3. Temperature control valve and cooling system

4. Oil return line and check valve

5. Air end internal components

This method saves time and avoids unnecessary disassembly.

Conclusion: How to Reduce High Oil Consumption Effectively

High oil consumption in screw air compressors is a common but controllable problem. In most cases, it is caused by worn consumables, poor sealing, high oil temperature, or blocked oil return paths.

To reduce the risk:

• Replace oil-air separators on time

• Use correct lubricant and change it regularly

• Control oil level and oil temperature

• Perform routine inspections and maintenance

By following these steps, technicians can greatly reduce oil consumption, protect compressed air quality, and ensure stable and efficient operation of screw air compressors.