18 
Fig. 11: Mass chromatograms of mass 231. Typical lubricating oil (same as in Fig. 8 upper 
right) compared to a typical crude oil (Oseberg crude) below. 
Fig. 12: Mass chromatograms of mass 231 of lubricating oils (same oils as in Fig. 8). 
A The lack of aromatic steranes in lubricating oils is an empirical finding: aromatic 
steranes have never been observed in any lubricating oil samples that have been 
analyzed for oil spill identification. An explanation could be that these compounds 
are removed from commonly used lubricating oils in de-aromatization processes. The clusters 
discernible in the 231-chromatogram probably represent 4a-M-steranes (mass fragment 231 
caused by an additional methyl group connected to the A-ring of the 217-mass fragment).