Absorption Wavebands for Discriminating Oxidation Time of Engine Oil as Detected by FT-IR Spectroscopy

Ali Abdul-Munaim,Dennis Watson,Torrey Holland,Poopalasingam Sivakumar

doi:10.3390/lubricants7030024

Abstract

Fourier Transform-Infrared (FT-IR) spectroscopy was used to analyze gasoline engine oil (SAE 5W20) samples that were exposed to seven different oxidation times (0 h, 24 h, 48 h, 72 h, 96 h, 120 h, and 144 h) to determine the best wavenumbers and wavenumber ranges for the discrimination of the oxidation times. The thermal oxidation process generated oil samples with varying total base number (TBN) levels. Each wavenumber (400–3900 cm−1) and wavenumber ranges identified from the literature and this study were statistically analyzed to determine which wavenumbers and wavenumber ranges could discriminate among all oxidation times. Linear regression was used with the best wavenumbers and wavenumber ranges to predict oxidation time.

Highlights

Oxidation is the primary driver of normal engine oil degradation [1] and a decreased lifespan [2].Oxygen and heat accelerate oxidation [3]
The purpose of this study was to take a fresh look at Fourier Transform-Infrared (FT-IR) for the discrimination and prediction of oxidation time using stastical criteria based on oil samples that were thermally oxidized for 0 h, 24 h, h, 72 h, 96 h, 120 h, and 144 h
total base number (TBN) decreased with oxidation time from 7.2 for fresh oil (0 h) to 1.8 after 144 h

Summary

Introduction

Oxidation is the primary driver of normal engine oil degradation [1] and a decreased lifespan [2].Oxygen and heat accelerate oxidation [3]. Oxygen free radicals interact with hydrocarbons breaking down hydrocarbon molecules and forming acidic compounds [1,4,5,6] that cause corrosion and deposits on metal surfaces. Additives added to base oil stock may constitute up to 30% (v/v) of engine oil [7]. Additives such as antioxidants and detergents retard the oxidation effect of engine oil becoming acidic. Antioxidants react with free radicals to form stable molecules instead of hydrocarbon breakdown [8]. Once antioxidants and detergent additives are consumed, sludge forms [4] and oil viscosity increases [6]

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Conclusion