The mean values of the metal contents found in the Lotos and Castrol oil samples
examined are listed in Tables 2 and 3. The results obtained, similarly to those presented
in Table 1, justify the statement that the metal contents of various fresh oils differ
significantly from each other. During consumption of the oils, their elemental compositions
changed further in regard to concentration of some metals only. However, the
observed differences were small in some cases. In both oils examined, the group of
metals originating from additives remained at approximately the same concentrations as
in the fresh oils, but the group of wear metals changed in concentration progressively