The present study is an analysis of the effectiveness of implementation of Six Sigma projects in an automotive company. The methodology employed is the DMAIC (Define, Measure, Analyze, Improve, Control) approach, which is integral to the application of the Six Sigma philosophy. The subject of the study comprised 56 projects implemented between 2020 and 2023 in a rubber seal manufacturing company. The analysis encompassed the identification of the quality tools utilized in the various phases of DMAIC, the types of errors addressed in the projects, and an assessment of their impact on ROI.A verification of the correlations between the number of tools employed and the parameters analyzed and the effectiveness of the projects was also conducted. The findings of these analyses enabled the identification of the pivotal tools and their combinations that contribute to the effectiveness of implementations in the various DMAIC phases. The results obtained provide practical guidance for industrial enterprises in optimizing improvement activities based on the Six Sigma methodology. Statistical verification demonstrated that the number of methods utilised did not exert a significant influence on ROI, while the number of parameters analysed did. Analysis of the DMAIC phases indicated that the analysis phase was the most critical for ROI, underscoring the significance of meticulous data analysis and the judicious selection of qualitative tools.