Study on the Impact of Naphtha and Light Fuel Oil on Key Quality Indicators of Gasoline and Diesel

The blending of naphtha and light fuel oil with gasoline and diesel during pipeline batch transportation poses risks of quality non-compliance. This study experimentally investigates the impact of these contaminants on key quality indicators to establish quantitative blending thresholds. Based on a volume-gradient experimental design (0–50 vol% for naphtha, 0–15 vol% for light fuel oil), diesel blends were tested for pour point, flash point, and 95% recovery temperature, while gasoline blends were tested for final boiling point, all in accordance with Chinese national standards. Results demonstrate that light fuel oil contamination in gasoline causes a linear increase in the final boiling point (y = 18.77x + 185.09, R2 = 0.91), exceeding the 205 °C limit at concentrations above 1.2 vol%. Naphtha contamination in diesel leads to a sharp linear decline in flash point (y = −13.20x + 101.83, R2 = 0.84), falling below the 60 °C threshold at concentrations above 3.0 vol%. Diesel pour point increases linearly with light fuel oil concentration (y = 0.39x − 26.41, R2 = 0.88) but remains within specification up to 15 vol%. These quantitative thresholds, derived from statistically significant regression models, provide a scientific basis for optimizing cut-point strategies and mitigating safety risks in product oil pipeline operations.