  This article presents the effect of the presence of solid contaminants, in
engine lubricating oil, on the tribological parameters, which impact negatively
on the performance of the engine and increase fuel consumption. This study
revealed that the lubricant was contaminated by Fe, Cu, Al, Pb and SiO2
particles. The tribological tests were performed using 0.63, 0.85 and 1.1 m s-1
average sliding speeds and 120 N contact load to mimic the boundary lubrication
regime of the sliding reciprocating motion of the piston ring/liner interface
in an engine. The presence of the solid contaminants in engine oils leads to an
increase in friction coefficient, wear and frictional power losses, increasing
the surfaces roughness as a consequence. The results showed that grain size and
concentrations strongly affected the tribological parameters. In order to
minimize the effect of solid contaminants, it is necessary to improve the
filtration accuracy for lubricating oils.

Applied Physics