Abstract: The physical and chemical properties of diesel engine oil after Mack T-12 engine test were analyzed. The ZDDP degradation was investigated by 31P-NMR spectroscopy. The lead corrosion of diesel engine oil and its influence factors were studied. The results showed the lead corrosion is related to oil degradation levels, the earlier the total base number and total acid number cross point appears during the test, the more severe lead corrosion. The lead corrosion is also related with ZDDP degradation rate, the lower the molar concentration of basic ZDP plus neutral ZDP in used oil, the higher degree of lead corrosion.

Key words: Mack T-12 engine test, diesel engine oil, lead corrosion, ZDDP, 31P NMR