The plastic packaging manufacturing industry is a downstream industrial sector, so far it has become the supply chain of customer products, especially being part of the food industry, pharmaceutical industry, cosmetics, and medical devices. With the increasing demand for plastic packaging, industry players are required to maintain the productivity and quality of the products they produce. In order to maintain product performance, control over the production process must be carried out, including maintaining engine performance. The effectiveness for measuring the performance of production machines is the OEE (Overall Equipment Effectiveness) indicator. The OEE value is influenced by 3 variables, namely availability, performance, and quality. These variables are translated into six big losses which consist of breakdown losses, set up and adjustment, start-up, idle and minor stoppage, speed losses, and defect losses. The purpose of this research is to analyze six big losses on blow molding machine units in plastic packaging manufacturing companies. The analytical method used in this study is to use a fishbone diagram and why why analysis to find out the cause of the low OEE value and use FMEA (Failure Mode and Effect Analysis) in determining corrective actions. Based on the results of the analysis, it was found that the first largest losses were breakdown losses with a value of 36.4% or 15,849 hours from. While the second losses are setup and adjustment losses with a value of 20.1% or 8,752 hours of machine operating time. Improvement efforts made are by performing autonomous maintenance, changing the frequency of PM (Preventive Maintenance), and making spare part stock planning by determining the minimum stock of spare parts. From the results of the improvements that have been made, it can be declared quite effective because the OEE value increased by 10.6%.