The effects of soot-contaminated engine oil on wear and friction: a review

During the diesel engine combustion process, soot particles are produced and are either exhausted into the atmosphere or absorbed by the engine's lubricant. Soot-contaminated lubricant has been shown to produce significant amounts of engine wear. The main mechanism of soot-related wear is through abrasion, but, at increased levels of soot content in the lubricant, starvation of the contact can occur, which can increase wear further. High concentrations of soot can increase the local acidic level and, around the piston where high temperatures and volatile gases coexist, corrosion may also occur. In this paper, the current understanding of engine wear due to soot contamination and the previous research performed is reviewed. The paper also discusses soot formation and its general effects within the engine (including friction and efficiency), as well as other issues including filtration or removal, effects on the lubricant, engine design and operation, and future industry targets and technologies related to soot contamination.