According to recent review published by Aucélio et al. [6], the majority of reported studies for determination of metals in lubricating oils are based on atomic spectrometry techniques. This fact is obviously due to the minimum pre-treatment of samples required by these spectrometric techniques, such as the dilution of lubricating oil in organic solvent, avoiding burning procedures for obtaining ash or digestion, which are lengthy and may be affected by the loss of analytes or by contamination.