Abstract: Methanol, as a clean energy source, holds promise as a key future energy support. However, the variation of key quality indicators during the storage of mixed oil, produced by interfacial cutting in the pipeline batch transportation of methanol and traditional oil products, remains unclear. Notable differences have been observed in the distribution characteristics of mixe doil at varying interface depths. This study focuses on methanol-diesel mixed oil, with regular sampling conducted at different depths across four mixed oil tanks. Key indicators such as density, flash point, and dynamic viscosity were monitored over time to systematically analyze the stability of quality indicators during storage. The results indicated that methanol-diesel mixed oil maintained overall temporal stability, though some parameters exhibited short-term fluctuations. Density at the same depth varied minimally, the flash point in diesel-dominant sections ranged from 13.0 ℃ to 31.5 ℃, and the viscosity change rate was -1.96%. The mixed oil exhibited vertical stratification and parameter differences across tanks. At the interface-where physical properties resemble diesel-density, flash point, and dynamic viscosity changed markedly, with variation rates around 2% be tween tanks. The research provides a theoretical foundation for managing methanol-diesel mixed oil storage in pipeline batch transportation and offers both theoretical support and practical guidance for safe tank operation, precise quality control, and optimized pipeline scheduling.