In order to offer the customer the opportunity to experience a differentiating after-sales service in the city of Quito, capital of Ecuador; a local automotive workshop introduces personalized service as a feat of professionalism, zero defects and quality. However, the improvement of lean post-sales processes through the DMAIC methodology has not been widely studied in the industry. This paper examines how to optimize processes in order to decrease the average service time of the workshop and increase the leanness of its activities and methodologies. Statistical analysis was used to determine the most relevant processes from the customer's point of view, with the support of the Contact Center database. Likewise, the circular DMAIC methodology was used with the support of Lean tools. The main results obtained show a reduction in time in the service process of the entire after-sales chain, a decrease in the waste of workshop supplies and / or materials and an increase in customer satisfaction evidenced in quality follow-up calls. Additionally, simulation and linear programming were applied.