The formulation of drilling mud is one of the most important aspects in drilling engineering. This is because the drilling muds are capable of lubricating and cooling the drill bit and drill string as well as carrying cuttings out of the borehole. All of these funtions require appropriate viscosity of drilling muds to facilitate pumping, circulate the cuttings and transfer them to the surface. Apart from that, adequate gelling property (gel strength) of the drilling muds is also required to prevent drill cuttings from settling down at the bit. Noteworthy, some of the chemicals or additives commonly used as a drilling mud gelling and viscosifying agents are carboxymethyl cellulose (CMC), xanthane and guar gum. However, these commercial drilling additives are subjected to thermal and biological degradation at temperature above approximately 120C. ViscoLigno has been formulated from oil palm lignocellulosic waste to overcome the obove shortcoming especially for deeper hydrocarbon wells. The rheological performances of the product as a drilling mud multi-functional agent showed that, ViscoLigno gave good gelling and viscocity building abilities at low dosage of 0.5 % w/w. ViscoLigno also can stand high temperature (200C which is equivalents to about 10 km depth) as a drilling mud gelling and viscosifying agent without the addition of other chemical. Moreover, this product capable of maintaining the pH of drilling mud at desired pH range of 8-10 at various temperatures without the use of pH controls agents; and not to mention that ViscoLigno is also able to act as a corrosion retardant agent for drill string and subsurface drilling equipments. These will definitely minimize the use of extra chemical while drilling, which will directly reduce the enviromental risk and at the same time reduce the cost of drilling operations.