Petroleum products. Determination of content of Benzo (a)pyrene (Ba P) & selected polycyclic aromatic hydrocarbons (PAH) in extender oils. Procedure using double LC cleaning & GC/MS analysis Petroleum products, Petroleum, Chemical analysis & testing, Lubricating oils, Oils, Aromatic compounds, Cyclic compounds, Determination of content, Extraction methods of analysis, Solvent extraction methods, Concentration (chemical), Precision, Reproducibility