Detailed analysis of lubricant deterioration using multiple analyzers

Significance of the Topic

Engine lubricants are critical for reducing friction, cooling, cleaning, and corrosion control in internal combustion and turbine engines. Monitoring lubricant condition helps prevent engine wear, avoid unplanned downtime, and extend service intervals by detecting chemical degradation, additive depletion, and contamination before performance falls below safe limits.

Objectives and Study Overview

This study demonstrates a comprehensive analytical workflow using Fourier transform infrared spectroscopy (FT-IR), gas chromatography with backflush (GC-FID), and inductively coupled plasma atomic emission spectrometry (ICP-AES) to assess lubricant deterioration. Two commercial lubricants (10W-60 and 0W-20) with different service histories were evaluated under ASTM standard protocols to track oxidation, nitration, fuel dilution, and element concentrations of wear metals and added performance agents.

Methodology and Instrumentation

The analytical approach combines three techniques:

• FT-IR analysis using a compact IRSpirit spectrometer with a liquid cell for rapid detection of oxidation (carbonyl absorption ~1750 cm^–1), nitration (1650–1600 cm^–1), sulfate by-products, water (broad OH band), and soot contamination.
• GC-FID with a Shimadzu GC-2030 system equipped with backflush capability and SH-Rxi-1ms column to quantify fuel dilution by measuring retention of n-C12 (gasoline) and n-C20 (diesel) in under 2–4 minutes (ASTM D7593).
• ICP-AES using the Shimadzu ICPE-9820 to determine 22 elements (ASTM D5185 and D4951), including wear metals (Fe, Al, Cu, etc.) and additive elements (Zn, Ca, B, etc.), in organic-solvent-diluted samples without requiring oxygen addition.

Used Instrumentation

• Shimadzu IRSpirit FT-IR spectrometer with Pearl liquid analyzer cell
• Shimadzu GC-2030 AF/AOC-20i FID with SH-Rxi-1ms column and backflush system
• Shimadzu ICPE-9820 simultaneous ICP-AES

Main Results and Discussion

• FT-IR detected significant oxidation and nitration in heavily used oil, while antioxidant-protected oil showed minimal oxidation peaks and stable nitrate bands.
• GC-FID backflush delivered rapid fuel dilution measurements with repeatability (%RSD ~2.3) over 600 consecutive analyses, demonstrating high throughput and reliability.
• ICP-AES achieved near-100% recoveries in spike-and-recovery tests for low- and high-concentration elements, confirming accuracy without oxygen flow, and enabled precise quantification of wear metals and additive depletion.

Benefits and Practical Applications

The integrated method offers:

• Fast, reproducible diagnostics with minimal sample preparation
• Simultaneous assessment of chemical and mechanical degradation pathways
• Compliance with established ASTM standards for lubricant health monitoring
• Cost-effective routine screening suitable for QA/QC and maintenance departments

Future Trends and Potential Applications

Emerging developments may include inline sensor integration for real-time lubricant monitoring, miniaturized portable analyzers for field testing, and advanced data analytics or machine learning models to predict remaining useful life based on multi-parameter data sets.

Conclusion

The combination of compact FT-IR, rapid GC-FID backflush, and oxygen-free ICP-AES provides a robust, standards-compliant toolkit for comprehensive lubricant condition assessment. This approach enables early detection of deterioration, optimized maintenance schedules, and improved engine reliability.

References

• ASTM E2412-10: Standard Practice for FT-IR Analysis of Lubricants
• ASTM D7593-14: Standard Test Method for Fuel Dilution in Used Lubricants by GC-FID with Backflush
• ASTM D5185-18: Standard Test Method for Multielement Analysis of Used and Unused Lubricating Oils by ICP-AES
• ASTM D4951-14: Standard Test Method for Trace Elements in Lubricating Oils by ICP-AES