The consumption of lubricating oil during the normal operation of an engine is inevitable, and the consumed lubricating oil can impact the engine’s particulate matter (PM) emissions after participating in the combustion process. This paper utilizes a particle size analyzer to conduct research on a direct injection diesel engine, focusing on the effects of lubricating oil and its additives on the size distribution of PM emissions. The results indicate that even a small amount of lubricating oil consumption during normal engine operation can affect the size distribution of PM emissions. Moreover, the traditional perception of lubricating oil quality does not directly correlate with its impact on PM emissions. Typically, CI-grade lubricating oil is considered to have a higher overall quality than CF-grade lubricating oil. However, under equivalent consumption levels, the PM emissions, in terms of peak height and number concentration in the size distribution, are less when using CF-grade lubricating oil compared to CI-grade lubricating oil.