Based on the "ASTM D7899-2013 Standard Method for Oil Stain Test of In-use Engine Oil Dispersion Performance", this article developed a new type of portable filter paper rapid oil spot production device. The experimental results show that the oil spot filter paper samples made by this device can The built-in standard legend and the corresponding expert judgment system can accurately judge the dispersion and quality decay of the engine oil in use, so as to judge the timing of lubricating oil replacement, which is simple and intuitive, and has good on-site guidance.