Diesel particulate filter(DPF) regeneration was carried out by in cylinder fuel post injection technology. The changed trend of oil viscosity and flash point were analyzed with different mass ratios between oil and diesel. Oil aging and fuel dilution were also researched by a special circle test. The volatilizations of diesel and oil were studied by thermo gravimetric analyzer. With the oil of the lower limit of viscosity

a liner scuffing test with the minimum clearance between liner and piston rings and a liner scuffing test at high temperature were performed. The results show that oil viscosity and flash point both decline following the growth of fuel dilution ratio. The fuel dilution ratio is 7% when the oil viscosity reaches the lower limit. The post-injection technology will not cause incomplete combustion or soot increase. With the increase of regeneration times

the oil viscosity decreases rapidly

and after 50 times of regeneration

the oil viscosity does not reach the lower limit. The thermo gravimetric curve demonstrates that the volatilizing temperatures of diesel and oil are quite different. Oil with 7% fuel will volatilize slightly at 120℃. The engine tier down inspection after the two liner scuffing tests shows that the main friction parts like cylinder liner

piston and piston rings do not appear abnormal wear

indicating that the engine has a low risk of liner scuffing.