T The success of oil and gas drilling operations is highly dependent on the performance of drilling mud. inadequate rheological properties reduce the mud\\\'s ability to transport drill cuttings, while excessive filtration loss and overly thick mud cake increase the risk of drill pipe sticking. to maintain drilling fluid performance, the industry commonly employs fluid loss control additives such as starch and polyanionic cellulose low viscosity (pac-lv). however, pac-lv is a relatively expensive imported product, whereas starch exhibits limited thermal stability at elevated temperatures due to starch granule degradation. meanwhile, indonesia has significant potential as one of the world\\\'s major cassava producers, with an annual production of approximately 7.9 million tons, making cassava starch a promising alternative additive that is more economical, environmentally friendly, and readily available.previous studies have demonstrated that cassava starch can reduce filtration loss, improve mud cake characteristics, and maintain rheological properties under certain testing conditions. however, its performance stability under simultaneous variations in concentration and temperature has not been comprehensively evaluated, and direct comparisons among starch, pac-lv, and cassava starch under identical operating conditions remain limited. therefore, this study aimed to evaluate the effects of additive type, concentration, and temperature on mud rheological properties, filtration loss, and mud cake thickness, as well as to determine the additive type and concentration that provide the most effective performance in maintaining rheological properties, minimizing filtration loss, and producing an optimum mud cake under various operating conditions. laboratory-scale experiments were conducted using a water-based drilling mud (wbm) formulated with bentonite, xcd, kcl, soltex, barite, biocide, and naoh, whose concentrations were kept constant for all samples. consequently, the only variables investigated were the type and concentration of the fluid loss control additive. three additives were evaluated at five concentrations (1, 1.5, 2, 2.5, and 3 g) and five aging temperatures (150°f, 175°f, 200°f, 225°f, and 250°f) following the api recommended practice 13b-1 testing procedure.the results showed that increasing additive concentration enhanced plastic viscosity (pv), yield point (yp), and gel strength for all additives, whereas increasing temperature reduced pv at the same concentration and decreased yp and gel strength due to thermal degradation, particularly at 225–250°f. pac-lv exhibited the highest rheological stability, maintaining pv, yp, and 10-minute gel strength within the recommended specifications across a wider concentration range, even at 250°f, whereas starch and cassava starch no longer satisfied these specifications. in terms of filtration performance, pac-lv was the only additive that achieved the target filtration loss of less than 10 ml/30 min, with the lowest value of 5 ml at a concentration of 3 g and 150°f. in contrast, starch and cassava starch did not achieve the target, with minimum filtration losses of 15 and 14 ml, respectively. mud cake thickness for all additives remained well below the recommended limit of 2 mm, with starch producing the thickest mud cake (0.70 mm), followed by pac-lv (0.65 mm), and cassava starch producing the thinnest mud cake (0.60 mm). pac-lv at a concentration of 3 g was identified as the optimum additive, particularly for maintaining rheological properties and controlling filtration loss over a wide temperature range. cassava starch at a concentration of 1.5 g and 175°f exhibited rheological performance closest to the recommended specifications among the natural additives; however, it still showed significant limitations in controlling filtration loss and maintaining long-term gel strength compared with starch and pac-lv. overall, this study concludes that pac-lv remains the most effective additive for applications requiring superior filtration loss control, while cassava starch has promising potential as a cost-effective and environmentally friendly alternative for low- to moderate-temperature drilling operations.