Preventive maintenance is an important strategy to improve physical availability, reduce downtime and extend equipment life. In the context of mining, transport fleets are large equipment and are subject to unplanned events that, in turn, interrupt operation and lead to unavailability. Therefore, the objective of this work is to analyze the main causes that influence the throughput of performance indicators of truck maintenance, focusing on the measurement of impacts caused by inefficiency of preventive maintenance. Thus, the data of 118 trucks were collected in 2022 and the performance calculated. The fleet CAT® 797F was prioritized was not adherent to the programmed, resulting in a production loss of 5,086,957 t o n s and, for maintenance, an unavailability was 9,722.88 h and 3,870 failures. Two evaluation requirements were proposed focusing on evaluating the notes and analyzing the adherence to the preventive. In summary, it was found that of the 783 scheduled preventive maintenance only 607 were performed and presented problems related to compliance with the guidelines. Finally, the inefficiency of the preventive ones generated an increase of more than 819 failures and an impact in the availability of 8.16%.