Energy efficiency saving and harmful emission reduction applications on marine vessels are quite valuable to achieving sustainable development goals highlighted by the IMO. In line with this goal, alternative fuels, and the WHRS have been utilized on the oil tanker in eight different scenarios since the attained EEXI and CII values of the oil tanker equipped with conventional systems don't meet the current regulations. The best performance has been obtained from scenario VII having a methanol-fuelled main engine and LNG-fuelled auxiliary engines with WHRS using the ORC. The attained EEXI of 3.543 and CII of 3.858 values have met current requirements and have kept the CII rating of the oil tanker at levels B to C. Scenario VII has also ensured roundly 31% cost advantage under the highest futuristic assumption of the carbon tax, this rate corresponds to $21M for approximately 5.5 years. As a result, all scenarios have provided superiority over the existing system in terms of meeting regulations, fuel consumption, carbon emission, and carbon tax. On the other hand, the utilization of carbon-neutral fuels in the main and auxiliary engines with the WHRS needs to be considered to comply with upcoming regulations and to achieve net-zero emission targets.