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Best practice for compressor oil changeover

A practical approach to system cleaning, lubricant selection, and long-term compressor reliability using Klüber compressor oils and Klüber Summit Varnasolv

Air and refrigeration compressors are critical to maritime operations. They support everything from onboard air systems and HVAC to cold-chain logistics, offshore process gas handling, and production equipment. When compressor performance deteriorates, the impact can be immediate: higher operating temperatures, unstable pressure, increased maintenance demand, and the risk of unplanned downtime.

Compressor oil plays a much broader role than lubrication alone. It removes heat, seals clearances, protects bearings and rotors, controls wear, and helps the compressor operate efficiently. Over time, however, high temperatures, oxidation, contamination, and degraded oil can create varnish, carbon deposits, sludge, and sticky residues throughout the oil circuit. These deposits can restrict oil flow, clog filters, shorten separator life, increase energy consumption, and raise the likelihood of equipment failure.

A compressor oil changeover should therefore be treated as a reliability intervention, not a simple drain-and-refill task. Done correctly, it helps remove degraded oil, release hidden deposits, reduce the risk of lubricant incompatibility, and prepare the system to achieve the full performance benefit of the fresh oil fill.

Why correct changeover matters

An incorrect changeover process can compromise compressor reliability and introduce avoidable operational risk. Common scenarios include using the wrong oil type, selecting the wrong viscosity, mixing incompatible lubricants, or failing to remove deposits before refilling the system.

Example Failure mechanism Operational impact Estimated cost

Wrong oil in use.

General hydraulic oil used as ISO VG 46 screw type compressor oil  
  • Insufficient oxidation resistance at discharge temperatures
  • Bearing lubrication film broke down
  • Bearing overheated and failed  
  • Emergency shutdown for 2~5 days
  • Loss of compressed air to production line  
   $35,000~$250,000 
Incorrect viscosity chosen  

 

  • Oil film too thin at normal operating temperature
  • Excessive oil mist passed through the separator
  • Instrument valves and pneumatic actuators contaminated
  • Sticky control valves
  • Excessive bearing wear due to inadequate lubrication
  • Unplanned maintenance  
   $20,000~$100,000 

Refrigeration compressor oil mismatch or mixing

POE oil topped up with mineral oil
  • Poor refrigerant and oil miscibility 
  • Evaporator oil logging
  • Lubricant starvation  
  • Complete refrigeration system shutdown
  • Cargo temperature excursions (reefer vessels)
  • Potential cargo claims
  $20,000–$500,000 
Mineral oil used to replace synthetic compressor oil  
  • Poor thermal stability and rapid oxidation
  • Varnish formation
  • High discharge temperature alarms  
  • Reduced platform production
  • Increased compressor oil consumption
  • Maintenance crew callouts
  $20,000–$100,000 

 

A well-planned changeover helps protect compressor reliability, reduce avoidable maintenance cost, and prevent claims or operational disruption during routine vessel operations. It requires both a structured workflow and the correct compressor oil for the application.

A holistic compressor oil changeover workflow

1. Diagnose before changing

Before changing the oil, review the compressor’s operating history and symptoms. Warning signs may include rising discharge or oil temperature, increasing oil filter or separator differential pressure, darkened oil, burnt odour, sticky residue, poor cooler performance, abnormal noise or vibration, and shortened oil life. Where possible, take an oil sample to assess oxidation, acidity, viscosity change, contamination, and deposit tendency. This will help determine whether a standard oil change is sufficient or whether system cleaning should be included.


2. Clean the system before the fresh oil fill

Where varnish, carbon build-up, sludge, or old-oil residue is suspected, cleaning should be part of the changeover plan. Klüber Summit Varnasolv is a concentrated cleaning fluid designed for screw-type compressors, hydraulic systems, gears, and other oil-circulating systems. It is added to the existing oil fill before the oil change, allowing deposits to be dissolved and suspended while the equipment continues operating.


Before dosing Varnasolv, confirm that the compressor can be operated safely and is in suitable mechanical condition. If time allows, an oil sample should be taken before cleaning to verify the oil condition and support the changeover decision.
As a practical guideline, drain approximately 10% of the existing compressor oil to create space, then add Klüber Summit Varnasolv at around 10% of the oil fill. Operate the compressor under normal conditions for the recommended cleaning period, typically 40–60 hours and not exceeding 80 hours, where possible at an operating oil temperature of 70–80°C. Always follow the latest safety data sheet, OEM instructions, and local safety procedures.


3. Drain thoroughly and remove contamination points

The success of the changeover depends on how thoroughly the old oil and suspended contamination are removed. Drain the compressor while the oil is warm after the cleaning process. Empty low points, oil cooler sections, lines, filter housings, separator vessels, and dead corners as far as practical. Replace oil filters and separators according to OEM recommendations. If heavy sludge or deposit release is observed, consider a short follow-up inspection or an additional cleaning step before the final refill.


4. Refill with the correct Klüber compressor oil

After cleaning and draining, refill the system with the selected Klüber compressor oil. The oil should match the compressor type, gas medium, operating temperature, OEM requirements, viscosity grade, and intended service interval. Use dedicated filling equipment where possible to avoid cross-contamination. Record the oil type, batch number, fill volume, operating hours, filter replacement, and baseline operating parameters. Wilhelmsen Ships Service provides access to the Klüber compressor oil range to support different compressor duties:

  • Air compressors: Klüber Summit SH series
  • Gas compressors: Klüber Summit PGS series, Klüber Summit PGI series, and Klüber Summit NGL 444 and 888
  • Refrigeration compressors: Klüber Summit RPE series, Klüber Summit RPT series, and Klüber Summit R 200


5. Verify performance after start-up

After restart, monitor oil temperature, discharge temperature, oil pressure, separator differential pressure, filter differential pressure, vibration, leakage, and overall compressor stability. A post-changeover oil sample after a short running period can help confirm that the system is clean and that the fresh oil is not being rapidly contaminated by residual old oil or deposits.

Best practice checklist
Plan the changeover during a controlled maintenance window, not after a failure event.
Review operating trends and oil analysis to identify varnish symptoms early.
Use Klüber Summit Varnasolv when deposits, sticky residues, sludge, or old-oil contamination are suspected.
Follow the recommended dosage, cleaning duration, temperature guidance, OEM instructions, and safety procedures.
Drain treated oil while warm and remove oil from low points, lines, filter housings, separator vessels, and dead corners.
 Replace filters and separators as required by OEM guidance.
Refill with the correct Klüber compressor oil for the compressor duty and operating environment.
Monitor post-changeover performance and establish the new oil fill as the baseline for future condition monitoring.


Compressor reliability does not come from the oil change alone. It starts with a well-designed changeover procedure, supported by the right cleaning agent, the correct lubricant selection, and disciplined post-changeover monitoring. A compressor oil changeover should be managed as a complete system-care process: Diagnose, Clean, Drain, Refill, and Verify. By combining Klüber compressor oils with Klüber Summit Varnasolv as a targeted cleaning step, operators can remove hidden deposits, protect the fresh oil fill, improve operating reliability, and reduce the risk of unplanned downtime.

Contact your WSS Technical representative for product selection guidance, changeover planning, and application support.

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