The Role of Lubricating Oil in Diesel Particulate and Particulate PAH Emissions

The role of lubricating oil in total particulate emmissions and in terms of polycyclic aromatic compounds (PAC) associated with the solvent organic fraction (SOF) of the particulate are investigated. Analysis of unused lubricating oil shows negligible concentrations of PAC. Used lubricating oil from a modified Perkins 4.236 Diesel engine, showed significant concentrations of PAC had accumulated in the oil in the form of PAC from unburnt fuel. Analysis of the oil was by gas chromatography using simultaneous parallel triple detection, allowing analysis of polycyclic aromatic hydrocarbons (PAH), nitrogen containing PAH (PANH) and sulphur containing PAH (PASH).

Motoring the engine in the absence of fuel enabled the contribution of lubricating oil to the exhaust particulate and particulate PAC emission to be determined. At high load and high speed the results indicated that the contribution of lubricating oil to the total exhaust particulate is over 40% and at low load and high speed reaches 70%. Analysis of the solvent organic fraction from the particulates using simultaneous parallel triple detection gas chromatography, revealed the presence of certain PAH which are also present in the lubricating oil. Thus the PAC content of the used oil acts as a source of PAC in particulate PAC emissions.