October 2, 2007
Lubricating oil may cause toxic emissions even in clean-burning engines, study suggests
Spokane, Washington – A new joint study by government and academic researchers in Washington and Minnesota suggests that lubricating oil may be an important but little-recognized source of toxic particle emissions from internal combustion engines. The study, published in the journal Environmental Science & Technology, says that most research focuses on diesel soot, rather than emissions from oil.
The report says that under normal diesel engine operation, trace metals are vapourized, and then absorbed or condensed onto the surface of soot particles. While the metals may be from the fuel, they more typically originate from lubrication oil on the cylinder walls or via blow-by in the combustion chamber.
The researchers modified a diesel truck engine to run on hydrogen, allowing them to focus solely on particle emissions from lubrication oil. They found that the hydrogen-powered engine emitted higher levels of metal-rich particles than the diesel-fuelled engine, and traced the lubrication oil as the primary source of the increased emissions. The particles identified included calcium, phosphorous, zinc, magnesium and iron, all of which have the potential for lung damage when inhaled over long periods.