Degradation Analysis of Lubricants Based on ASTM E2412 by Fourier Transform Infrared Spectrophotometer FTIR

Significance of the Topic

Lubricant condition monitoring is critical for maintaining engine performance, extending component life, and preventing downtime. Analyzing degradation and contamination provides actionable information on oil health, enabling timely maintenance and reducing operational costs.

Objectives and Study Overview

This study demonstrates a streamlined spectrophotometric approach for evaluating automotive engine lubricants according to ASTM E2412. By comparing new and used oils, the work aims to characterize chemical changes such as oxidation, nitration, and additive depletion using Fourier transform infrared (FTIR) spectroscopy.

Methodology and Instrumentation

Transmission measurements were conducted on an IRSpirit™-T FTIR spectrophotometer equipped with a Pearl™ horizontal liquid transmission accessory (100 µm path length). Key parameters included 4 cm⁻¹ resolution, 40 co-added scans, Happ–Genzel apodization, and a DLATGS detector. Two commercial engine oils (A: 10W-60, used 3 months/3 000 km at high rpm; B: 0W-20, used 1 year/5 000 km in urban driving) were analyzed alongside fresh samples for baseline comparison.

Main Results and Discussion

Infrared spectra revealed distinct degradation patterns:

• Lubricant A exhibited increased absorption bands corresponding to moisture, carbonyl groups (oxidation), and nitro functionalities (nitration).
• Lubricant B showed diminished antioxidant-related bands and emerging nitration signals, while oxidation bands remained suppressed—attributed to remaining antioxidant efficacy.

The Pearl™ accessory facilitated simple sample loading, minimized air bubble interference, and ensured consistent path length, resulting in reproducible and high-quality spectra.

Benefits and Practical Applications

FTIR analysis under ASTM E2412 enables rapid, non-destructive evaluation of lubricant health without sample pretreatment. The method supports:

• Routine monitoring of oil degradation in maintenance programs.
• Detection of early-stage chemical changes before mechanical damage occurs.
• Optimization of oil change intervals, reducing waste and costs.

Future Trends and Opportunities

Integration of automated FTIR sampling systems and advanced chemometric tools can enhance data interpretation and real-time monitoring. Combining FTIR with complementary methods (GC for soot analysis, ICP-AES for metal contaminants) in multi-modal platforms will provide comprehensive lubricant diagnostics, supporting predictive maintenance in smart manufacturing.

Conclusion

The study confirms that horizontal-cell FTIR analysis per ASTM E2412 is an effective, user-friendly approach for assessing lubricant degradation. The Pearl™ accessory’s ease of use and path-length stability yield reproducible data, making this method suitable for routine engine oil monitoring.

Used Instrumentation

• IRSpirit™-T FTIR spectrophotometer (KBr window plate)
• Pearl™ horizontal transmission accessory, 100 µm path length
• DLATGS detector

Reference

ASTM E2412: Standard Practice for Degradation Analysis of Lubricants by FTIR Spectroscopy