Diesel power generators have critical the task of providing electricity for industrial purposes, either as backup power or main power. One function that plays a very important role in ensuring the smooth implementation of production activities is the maintenance of machines and other production facilities. One of the maintenance methods that is often applied in various manufacturing industries is preventive maintenance. However, there is a limited study that evaluates the depth of common preventive maintenance implementation in Indonesia. This research is designed to fill the gap by evaluating and mapping the depth of preventive maintenance between the different sizes of diesel power generators. The research provides a summary of the depth of preventive maintenance implementation on conduct maintenance planning and scheduling, component replacement, condition monitoring, and maintenance evaluation. Moreover, there is no significant difference between the size of the diesel power generator and the percentage conducted maintenance aspect. So that it can be ascertained that all respondents from various types of manufacturing industries carry out preventive maintenance.Diesel power generators have critical the task of providing electricity for industrial purposes, either as backup power or main power. One function that plays a very important role in ensuring the smooth implementation of production activities is the maintenance of machines and other production facilities. One of the maintenance methods that is often applied in various manufacturing industries is preventive maintenance. However, there is a limited study that evaluates the depth of common preventive maintenance implementation in Indonesia. This research is designed to fill the gap by evaluating and mapping the depth of preventive maintenance between the different sizes of diesel power generators. The research provides a summary of the depth of preventive maintenance implementation on conduct maintenance planning and scheduling, component replacement, condition monitoring, and maintenance evaluation. Moreover, there is no significant difference between the size of the diesel power generator and the percentage conducted maintenance aspect. So that it can be ascertained that all respondents from various types of manufacturing industries carry out preventive maintenance.