This study investigates the influence of varying aging processes on the rheological behavior and microscopic features of bio-based recycled asphalt, focusing on the utilization of Waste Cooking Oil (WCO) as a rejuvenator. The research evaluates the rheological and fatigue characteristics of the modified binder, alongside a detailed microscopic analysis to determine the molecular composition changes in both aged and recycled asphalt. The incorporation of WCO was found to compromise rutting performance slightly, yet significantly enhance fatigue resistance and reduce susceptibility to low-temperature cracking. With the progression of aging, an increased dosage of WCO effectively mitigated the negative impacts, bringing the molecular composition and functional groups of the aged asphalt closer to that of the original material. Despite these improvements, a full restoration to the asphalt’s original properties remained elusive. These findings underscore the potential of waste bio-oil as a sustainable resource for enhancing the durability and environmental friendliness of asphalt pavements.