Quantification of Biofuel Components in Automotive Lubricants

Small amounts of diesel fuel can accumulate in engine oils during the normal operation of an engine. Biofuels such as fatty acid methyl esters (FAMEs), due to their higher boiling points, are rather more persistent. This leads to much higher levels of fuel dilution and is one of the main factors having an influence on the condition of used engine oil. As the use of biofuels in the automotive sector becomes more widespread, the need to assess fuel dilution levels as well as fuel and lubricant quality is of increasing importance. In this study, fuel dilution levels in lubricants have been quantified using proton nuclear magnetic resonance (1H NMR) method and correlated with the data obtained by a gas chromatography (GC) technique. Specifically, the amount of FAME has been quantified in both fresh and in selected used oil samples.

The results of this study show that fuel dilution levels can be quite reasonably quantified using the GC and 1H NMR techniques. Both techniques provide information on the type of oxidation by-product species present in the aged oils. Advantages and disadvantages of each method are detailed and a preference for one technique is expressed.