<p>The suspension stability and rheological properties of high-density oil-based drilling fluids present significant challenges under high-temperature conditions. To mitigate these issues, researchers indicate that the selection and treatment of weighting materials play a pivotal role in stabilizing such fluids under extreme conditions. Accordingly, to optimize the weighting materials dispersion and thermal stability, a novel wettability modifier (MSP) was synthesized to enhance oil-phase compatibility. The surface properties, particle size distribution, and charge characteristics of four weighting materials were characterized using FTIR, particle size distribution analysis, zeta-potential measurements, and microstructure examination. Experiments assessing suspension stability (static/dynamic sag) and rheological properties were conducted at 160&#xa0;°C. The results demonstrated that MSP significantly improved weighting material dispersion, particularly after high-temperature aging. The suspension volume of manganese ore fine in diesel oil approaches 100% after standing for 24&#xa0;h. Based on these findings, a blended weighting material consisting of micronized barite and manganese ore fines (at a 1:3 mass ratio) was formulated, producing fluids with densities ranging from 2.2 to 2.5&#xa0;g/cm³. After aging at 160&#xa0;°C for 16&#xa0;h, the resulting fluids exhibited a sag factor is equal to 0.5, the flow behavior index (n) less than 1, indicating exceptional sag stability and maintained acceptable rheological properties.</p> Graphical abstract <p></p>