The wear of piston rings in the diesel engines with EGR system is studied experimentally. In order to clarify the effect of PM on the wear, the wear of the piston rings in the test engine is measured,
(1) when the non-soluble in the lubricating oil is removed by the oil filters,
(2) when PM in the re-circulating gas is removed by the DPF,
(3) when the carbon black is added in the lubricating oil.
The experimental results are discussed with the measured time history of kinematic viscosity, total base number, total acid number, ZDTP survival rate, and carbon residual content and its particle size in the engine oil.