HEADSPACE GAS-CHROMATOGRAPHY ANALYSIS OF UNCOMBUSTED GASOLINE DILUENT IN USED GASOLINE-ENGINE OILS

A method for analyzing the uncombusted gasoline diluent in used gasoline engine oils using a combination of headspace gas chromatography (GC) and PONA (Paraffins, Olefins, Naphthenes and Aromatics) analysis was studied. The gasoline diluents in ten types of used gasoline engine oils, taken from engines submitted to road, bench, and chassis dynamometer tests, were determined using headspace gas chromatograms after their peak intensities had been corrected according to their retention indices. These results were compared with those from ASTM D3525 to assess the appropriateness of the headspace GC method. A further attempt was made to analyze corrected headspace gas chromatograms by PONA analysis in order to determine the diluting components in the used engine oils. The results of the study revealed that there was no reason to think that the sample would decompose when injected into GC apparatus, and that the information on the gasoline diluent and its diluting components should be readily obtainable. Analysis showed that the diluting components of uncombusted gasoline consisted mainly of less combustible gasoline components.