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2.4.1 Analysis 
2.4.1.1 GC screening 
According to the boiling ranges of the products involved, different regions overlap, and thus 
different overlays are produced when bunker oils and lubricating oils are mixed. In Figure 25, 
GCs of a light fuel oil (above) and a heavy fuel oil (below) are given together with the GCs of 
3 different grades of lubricating oils (90 cSt, 150 cSt, 600 cSt). 
Fig. 25: GCs of a typical light fuel oil (upper) and a typical heavy fuel oil shown together with 
the GCs of 3 different lubricating oils. The main boiling range of the biomarkers is 
indicated by the two lines. 
Mixtures of light fuel oil and lubricating oil are normally easily detected because of the 
different boiling ranges of the two products involved (Figure 24). 
2.3.1.2 GC-MS analysis 
As can be seen in Figure 25, the resulting compound patterns of the biomarkers of bunker 
oil/lubricating oil mixtures are influenced differently by the corresponding patterns of the 
individual pure products. Because of the limited boiling range of light fuel oil, biomarkers in 
light fuel-/lubricating oil mixtures originate nearly completely from the lubricating oil part. 
Therefore, even the presence of small amounts of lubricating oil can be detected in a light 
fuel-/lube oil mixture. Figure 26 shows the hopanes and aromatic steranes of the last 4 oils 
given in Figure 24. While the relatively small amount of lubricating oil is hardly detected in 
Figure 24 g), for example, the biomarker patterns of this sample are strong evidence of the