Evaluating the Use of Recycled Hydraulic Oil in Heavy Equipment

[MikePhua]

Understanding Recycled Hydraulic Oil
Recycled hydraulic oil—also known as re-refined oil—is produced by collecting used lubricating oils and processing them through filtration, dewatering, vacuum distillation, and chemical treatment to remove contaminants. After refining, the oil is often blended with additive packages to restore or enhance its performance properties.
The final product can meet or even exceed the specifications of virgin oil, depending on the quality of the re-refining process and the base stock recovery. However, skepticism remains widespread among equipment operators and technicians, particularly in applications involving high-pressure, temperature-sensitive hydraulic systems.
How Hydraulic Systems Depend on Oil Quality
Hydraulic oil performs multiple critical functions:

• Power Transmission: Transfers energy throughout hydraulic circuits
  
• Lubrication: Minimizes friction between internal components
  
• Cooling: Carries heat away from pumps and valves
  
• Contamination Control: Holds and transports particulates to filters
  
• Sealing: Helps maintain pressure by reducing internal leakage
  

Because of these roles, even small changes in oil viscosity, oxidation resistance, or additive breakdown can directly impact system performance, particularly in tightly-toleranced components like:

• Piston pumps
  
• Servo valves
  
• Hydrostatic drive motors
  
• Load-sensing systems
  

Common Concerns with Recycled Oil
Skeptics of recycled hydraulic oil often cite concerns such as:

• Residual Contaminants: Worry that metals, sludge, or water may remain
  
• Additive Depletion: Uncertainty about how well additives are restored
  
• Oxidation Stability: Fear that re-refined oil may break down faster under heat
  
• Warranty Validity: Equipment OEMs may not endorse non-approved oils
  
• Inconsistency: Variation between batches or brands of recycled oil
  

These concerns are particularly pronounced in extreme-use applications, such as:

• Forestry equipment operating in hot or damp environments
  
• Excavators in mining sites exposed to heavy particulate load
  
• Precision-control systems in modern hydraulic cranes
  

Counterpoint: The Science Behind Re-Refining
The re-refining process today is far more sophisticated than it was decades ago. Modern plants use:

• Vacuum distillation to separate base oils from contaminants without thermal cracking
  
• Hydrotreating to remove sulfur, nitrogen, and aromatics
  
• Additive packages that restore anti-wear, anti-foam, and rust-prevention properties
  

According to ASTM and API standards, Group II and Group III base oils from re-refining can match virgin oils in purity and viscosity index. In fact, some major oil brands quietly blend re-refined base oils into their products—even for new oil.
Real-World Example: Municipal Fleet Success
A city public works department in the Midwest switched its hydraulic fleet—including garbage trucks, snow plows, and lift equipment—to a certified re-refined hydraulic oil supplier. After strict oil analysis protocols, they reported no increase in wear metals or failure rates over a five-year trial period. Savings from bulk pricing and environmental incentives helped fund new diagnostics tools for their maintenance shop.
Key Factors When Considering Recycled Hydraulic Oil
For those considering the switch, the following points should be carefully evaluated:

• Certification Standards
  • Look for oils meeting ISO 11158, DIN 51524, or OEM-specific standards (e.g., CAT HYDO, John Deere JDM J20C)
    
• Supplier Reputation
  • Work with known suppliers who disclose their additive chemistry and quality control process
    
• Oil Analysis Program
  • Regular lab testing helps detect early signs of oxidation, additive depletion, or contamination
    
• Application Environment
  • Avoid use in critical, high-precision systems unless proven performance is available
    
• Warranty Review
  • Confirm with OEMs whether use of re-refined oil voids warranties or service agreements
    

Terminology Clarification

• Re-Refined Base Oil: The oil recovered from used lubricants through industrial processes
  
• Additive Package: Chemical blend added to base oil to enhance performance (anti-wear, detergent, viscosity stabilizer)
  
• Oxidation Stability: Resistance of oil to breakdown when exposed to heat and oxygen
  
• Viscosity Index (VI): Measure of how much oil viscosity changes with temperature; higher VI = more stable
  

Historical Note: Wartime Recycling and Industrial Shifts
Re-refining is not new. During World War II, military forces in Europe and North Africa often recycled engine oils from damaged or abandoned vehicles to support ongoing operations. What began as necessity slowly evolved into an industrial process. In the 1970s oil crisis, many North American industries invested in basic re-refining technology. However, it wasn’t until environmental legislation and closed-loop recycling programs matured in the early 2000s that recycled oil regained industry-wide attention.
Conclusion
Recycled hydraulic oil, when produced and tested to modern standards, can be a viable and cost-effective solution for many applications. While concerns about contamination and performance longevity are valid, rigorous supplier selection, oil analysis, and a clear understanding of system requirements can help operators make informed decisions. In many cases, especially in non-critical environments, re-refined oil offers both environmental and financial benefits without sacrificing equipment reliability. As with any fluid choice, knowledge, context, and data-driven maintenance remain key.