The ASEAN's legislation has become more regulatory towards electric vehicles for automotive manufacturers to ensure the environment is preserved better for future generations. The ASEAN roadmap 2025 requirement in optimizing a conventional vehicle's fuel consumption is implemented with hybrid technology in targeting the automotive industry worldwide to achieve energy-efficient vehicles. This research aims to develop a vehicle model via 1D simulation cycle and implement the 48V mild hybrid to lower vehicle fuel consumption considering perspective in drive cycles data. The vehicle model used in this research is a D-segment vehicle powered by a 1.8L TGDI engine. The base model will be created using a GT Suite software where data is compared and analyzed with actual vehicle measurement. There will be two models produced; with and without Belt-Alternator-Starter (BAS) system. They will be further investigated for their functions based on NEDC and RDC drive cycles for fuel consumption. However, implementing the add-on technology from this simulation improved overall vehicle fuel consumption by 7.7% in NEDC and 1.7% in RDC. The results obtained for the optimization of the vehicle have shown difference by the results of each engine characteristics such as engine fuel flow rate, speed, torque, the BAS functions, and state of charge. The research proposes its findings to understand the practical usage of 48V mild hybrid system in fuel reduction and provide reliable proof to use as a reference for initiative studies.