How to Troubleshoot and Fix Abnormally High Oil Consumption in Air Compressors

A small increase in oil consumption may be hiding a big problem.

During air compressor operation, abnormally high oil consumption is a common issue. It not only increases operating costs but may also serve as an early warning of potential equipment failure. How should you troubleshoot the problem systematically and fix it effectively?

**01

How to Determine Whether Oil Consumption Is Abnormal**

For a normally operating screw air compressor, oil consumption typically does not exceed 1–2 liters per 1,000 hours. If consumption suddenly increases to 5 liters or more, or if the oil level drops from MAX to below MIN within 10 days, it can be considered abnormal.

A simple and practical way to check:
Hold a clean white paper at the compressor’s discharge outlet for 10 seconds. If obvious oil spots appear, the oil content in the compressed air is too high. Under normal conditions, the paper should show little to no oil residue.

Other signs during routine inspection include:

• Oil contamination inside downstream pneumatic tools or dryers

• Oil spraying or oil leakage during operation

These are strong indications of excessive oil consumption.

**02

Common Causes of Increased Oil Consumption & Troubleshooting Methods**

1. Oil-Air Separator Issues
This is the primary cause of increased oil consumption. When the separator is used for too long (over 2,000 hours) or when low-quality products are used, the filter material pores enlarge or rupture, reducing separation efficiency.
Troubleshooting: Check separator differential pressure, which should be ≤0.1 MPa.

2. Oil Return System Blockage
If the check valve in the oil return line is stuck by foreign matter or the return filter is clogged, separated oil cannot return to the airend.
Solution: Disassemble the oil return assembly and clean carbon deposits with kerosene.

3. Minimum Pressure Valve Failure
If the valve leaks or opens too early (normal opening pressure: 3.5–5.5 kg/cm²), pressure buildup time increases, causing high oil mist concentration and increased separator load.

4. Abnormal Operating Parameters

• Discharge pressure exceeding the rated value by more than 10%

• Long-term low-load operation (load rate <30%)

Both will affect oil separation performance.

5. Overfilling Lubricating Oil
If the oil level exceeds the MAX mark, the rotating rotor stirs the oil and generates excess oil mist, surpassing the separator’s capacity.

**03

Solutions to Reduce Excessive Oil Consumption**

Emergency actions:

• Check oil level; if above MAX, stop the compressor, release pressure, and drain to the correct level.

• Inspect the oil return line and clean the check valve and filters.

• Use compressed air (≤0.3 MPa) to clean the air filter; replace it if heavily blocked.

• Adjust discharge pressure to the rated range and observe consumption for 1–2 hours.

Deep repair actions:

• Replace the original oil separator element and sealing gaskets; tighten bolts diagonally and evenly during installation.

• Inspect and replace shaft-end seals and aged oil hoses, ensuring proper sealing of tank welds and flanges.

• Adjust operating strategy for compressors running long-term at low load to avoid low-efficiency conditions.

• Optimize system pressure using a pressure regulating valve to avoid operating beyond the designed range.

• Use high-quality screw compressor oil of the correct viscosity; avoid mixing different oil types.

• Match compressor capacity with actual air demand to prevent operating with an oversized machine.

**04

Effective Measures to Prevent Increased Oil Consumption**

1. Standardize consumable selection and replacement
Use lubricants specified in the manual. Replace oil separator elements every 2,000–3,000 hours and replace seals annually as preventive maintenance.

2. Establish routine inspection cycles

• Daily: check oil level and discharge pressure

• Weekly: check oil pipe connections and sealing

• Monthly: test separator differential pressure and oil content in compressed air

3. Optimize operating and maintenance practices

• Use a fuel container with a filter to prevent impurities from entering during refilling

• After replacing the oil separator, release air from the tank before starting the machine

• Clean the oil tank every six months to remove sludge and carbon buildup

4. Set proper operating parameters

• Avoid setting discharge pressure too high

• Reducing compressor pressure by 1 bar can save 7%–10% energy

• Ensure the compressor operates near its rated conditions, avoiding long-term low-load or overload operation

Abnormally high oil consumption should never be ignored. Systematic troubleshooting, prompt corrective actions, and preventive maintenance are the keys to resolving the issue. By applying scientific methods and standardized practices, oil consumption can be kept within a reasonable range, ensuring stable and reliable compressor operation.

Prevention is better than cure—a well-maintained compressor is the best way to avoid excessive oil consumption.