Total base number (TBN) in used motor oil

Importance of the Topic

Accurate determination of total base number in used motor oil is essential for monitoring additive depletion, assessing oil degradation and ensuring engine performance and longevity.

Objectives and Study Overview

The study aims to establish a reliable titrimetric procedure using trifluoromethanesulfonic acid in glacial acetic acid with isobutyl vinyl ether to enhance endpoint detection and to demonstrate repeatability of the method on new and aged motor oil samples.

Methodology and Instrumentation

• Reagents and Solutions
  • Titrant: 0.1 mol/L trifluoromethanesulfonic acid in glacial acetic acid
  • Indicator: isobutyl vinyl ether
  • Solvent: anhydrous toluene
• Sample Preparation
  • Weigh 2 g of fresh oil or 3 g of used oil into a clean, dry titration vessel
  • Add 40 mL of dry toluene and 1 mL of isobutyl vinyl ether
• Instrumentation
  • 859 Titrotherm with endothermic detection
  • 814 USB Sample Processor
  • 800 Dosino dosing units (titrant, indicator, solvent)
  • 802 Rod Stirrer and 96 mm propeller
  • Thermoprobe and Titrotherm titration head
• Titration Parameters
  • Stirring rate: 12
  • Dosing rate: 2 mL/min
  • Pause time: 20 seconds
  • Evaluation starts and damping at 0.2 mL addition
  • End point criterion based on a 120 μW thermal signal change

Main Results and Discussion

The method yielded a total base number of 4.73 mg KOH per gram of sample with a relative standard deviation of 0.60 percent (n equals 3). The endothermic endpoint detected by the Titrotherm provided clear and reproducible titration curves, illustrating reliable performance across fresh and used oil samples.

Benefits and Practical Applications

This approach requires minimal sample preparation, uses selective reagents that avoid strong oxidizers, and offers automation capabilities for high throughput laboratories. It supports quality control in oil analysis, additive monitoring and regulatory compliance in automotive and industrial settings.

Future Trends and Applications

Advances may include inline titration systems for real-time monitoring, miniaturized sensor integration for field testing, alternative thermal or spectroscopic endpoint detection and software-driven data analytics to streamline maintenance schedules and predictive engine diagnostics.

Conclusion

The described titrimetric procedure for determining total base number in motor oils is robust, precise and suitable for routine laboratory use, providing critical information on oil condition and additive performance.

References

• Greenhow E. J., Spencer L. E. Chemical Industry London 466 1972