Overall, HTGC-MS was determined to be a valuable comparative technique for the analysis of motor oils. By examining the unresolved envelope, the resolved hydrocarbons, and the smoothed total ion chromatograms (TICs), 32 of the 34 oil brands and grades were distinguished from one another. Although labeled brand and labeled SAE-grade identification were not possible due to complicated manufacturing and distribution processes, there was a trend in the shape of the unresolved envelopes. As the viscosity of the oils increased from 5W to 10W to 20W, the retention times lengthened and the envelopes broadened. Unused oils of the same brand and viscosity, but from different stores, could not be differentiated. Oil samples were collected from the dipsticks of 30 vehicles and produced 26 distinct TICs. Only by smoothing the TICs and comparing the shapes of the unresolved envelopes were several of these chromatograms differentiated from one another. The samples consisted of 9 brands, 10 SAE grades, 4 fully synthetic oils, and 4 partially synthetic blends. Oil samples were collected from 30 cars by swabbing the crankcase dipstick with a cotton-tipped swab. The analysis was conducted on a PerkinElmer Clarus 500 Gas Chromatograph-Mass Spectrometer with a PTV injector. TurboMass version 5.0 from PerkinElmer was used for data analysis. Smoothing of the chromatogram allowed for better visualization and comparison of the shape of the unresolved envelopes. 3 tables, 16 figures, and 22 references