Reusing Hydraulic Oil in Heavy Equipment: Risks, Rewards, and Real-World Practices

[MikePhua]

Why Reuse Hydraulic Oil?
Hydraulic oil is the lifeblood of heavy machinery, enabling precise movement, power transmission, and component lubrication. With rising costs and environmental concerns, many operators consider reusing hydraulic oil—especially in low-demand systems like chain boxes or auxiliary compartments. But is it safe?
Terminology Notes

• Hydraulic Oil: A specialized fluid used to transmit power in hydraulic systems, often containing anti-wear, anti-foam, and anti-corrosion additives.
  
• Chain Box: A compartment housing drive chains, typically requiring basic lubrication rather than high-pressure fluid dynamics.
  
• Hy-Gard: A proprietary hydraulic/transmission oil developed by John Deere, known for its additive package and compatibility with various systems.
  
• Oil Contamination: The presence of water, metal particles, dust, or degraded additives that compromise oil performance.
  

Field Insight: A JD 570A Grader Case
A retired geologist operating a John Deere 570A grader faced a decision: reuse dark but seemingly intact hydraulic oil from the transmission in the chain boxes. The grader saw less than 100 hours of use per year, and the chain boxes required 10 gallons of Hy-Gard—exactly what was drained from the transmission.
His reasoning was sound:

• Chain boxes operate under low pressure and low thermal stress.
  
• The oil had been regularly topped off with fresh Hy-Gard.
  
• The cost and logistics of recycling 10 gallons of oil were nontrivial.
  

Expert Opinions and Practical Wisdom
Experienced mechanics chimed in with supportive views:

• Viscosity is key: As long as the oil maintains proper viscosity and cleanliness, it’s suitable for chain lubrication.
  
• Chain lubrication is forgiving: Unlike hydraulic pumps, chains need only to stay wet and free of debris.
  
• Dust control matters: Keeping the chain box sealed and clean is more critical than oil freshness.
  

One operator recalled chaining all four tandems for snow plowing—a task that stresses chain boxes. He emphasized the importance of preventive maintenance over oil purity in such systems.
Industry Practices and Broader Context
Reusing hydraulic oil is not uncommon in industries with large fluid volumes. In power generation, oil tanks holding thousands of gallons are routinely filtered and reused. The key lies in:

• Filtration: Removing particulates and water using vacuum dehydration and fine-micron filters.
  
• Additive monitoring: Ensuring essential additives remain intact after filtration.
  
• Oil analysis: Lab testing for acidity, oxidation, and contamination levels.
  

According to Oil Filtration Systems, reclaimed oil can meet or exceed OEM cleanliness specs if properly treated. Their systems reduce water content from over 2,000 ppm to under 200 ppm and particulate levels to ISO 16/14/12.
Case Study: Industrial Reclamation Success
A plastics manufacturer in Ohio reclaimed hydraulic oil across three facilities, cutting oil costs by 60% without increased pump or valve failures. Their success hinged on:

• A robust sampling program
  
• Partnering with a reclamation company for detailed testing
  
• Using virgin oil only to supplement reclaimed stock
  

Risks and Considerations
Despite the benefits, reusing hydraulic oil carries risks:

• Additive depletion: Filtration may remove anti-foam or anti-wear agents.
  
• Water contamination: Even small amounts can cause corrosion and cavitation.
  
• Acid buildup: Over time, oil can become acidic and damage seals.
  

Experts recommend starting small—test reclaimed oil in non-critical systems like chain boxes or auxiliary tanks before expanding to high-pressure hydraulics.
Conclusion: A Balanced Approach
Reusing hydraulic oil is a viable strategy when done thoughtfully. For low-demand systems like chain boxes, the practice can save money and reduce waste without compromising performance. However, success depends on:

• Understanding system demands
  
• Monitoring oil condition
  
• Applying proper filtration and testing
  

As one seasoned operator put it, “Oil doesn’t wear out—it gets dirty. Clean it right, and it’ll keep working.”