[en] The 300 MW unit of a power plant is resistant to fuel, and its color is reddish brown. The acid value and resistivity are in line with the standard requirements. However, a large amount of sludge appears in the same grade of oil, causing the filter to be blocked and unable to supply oil. After the oil is filtered by the online oil filtering device, the degraded anti-fuel oil and the new oil are mixed and there is still sludge. In order to solve this problem, the components in the anti-fuel oil were tested and the acid value, moisture, resistivity, particle size and sludge precipitation test were tested. The cause of the sludge in the mixed oil was found and the treatment method was found. The oil samples were adsorbed by diatomaceous earth, activated clay and strong polar silica-alumina, and the parameters were analyzed after treatment. It was found that both activated clay and polar silica-alumina adsorbent have better purification functions, but the polar silica-alumina adsorbent is better and effectively solves the problem of fuel resistance degradation. (paper)