<p>This study investigates the seismic response of an oil refinery steel building equipped with viscoelastic (VE) materials as base isolators. The primary objective is to evaluate the effectiveness of six VE materials - High-Damping Rubber (HDR), Butyl Rubber, EPDM (Ethylene Propylene Diene Monomer), Neoprene, Silicone Rubber, and Polyurethane (PU)-when used as base isolators in a six-storey oil refinery structure. A comparative analysis was conducted between two support conditions: a fixed base and a base isolated with VE materials. Numerical simulations were performed using ETABS to assess key seismic performance parameters, including natural period, story displacement, story drift, base shear, and plastic hinge formation through modal analysis, response spectrum analysis, and pushover analysis. Additionally, ABAQUS Explicit was employed to analyse the VE materials under cyclic loading, evaluating their energy dissipation capacity and hysteretic behaviour through force-displacement curves. The results show that VE base isolators significantly increase the natural period of the structure, reducing seismic demands. Cyclic loading tests confirmed that VE base isolators exhibit stable hysteresis loops and high energy dissipation efficiency, making them a reliable solution for seismic mitigation.</p>