This paper examines the pivotal role of high-quality aftersales service in maintaining global automotive industry competitiveness and sustainability. It presents the methodology for utilizing lean principles in sustainable performance improvement by identifying and eliminating waste in aftersales processes. The approach is exemplified through a case study in road freight vehicle service and maintenance using process mapping. The methodology involves developing a comprehensive process map, analyzing current inefficiencies, and proposing improvement measures. The methodology enhances operational efficiency and contributes to sustainable performance in terms of economic, environmental, and social factors. The methodology is generalized and outlines successful improvement phases and sub-steps.