Nowadays the actual problem is an individual approach to optimization and rationalization of machine use parameters. As to individual reliability indices, one of the ways to improve the operation of the machine and tractor park is the choice of the rational service life of tractors. According to the proposed model, it is reasonable to take the tractor out of service when it becomes unprofitable. To verify the proposed model, 10 hauler tractors of 3,0 category, operated in the agricultural enterprises of the Vologda district, Vologda region were subjected to studying during five years. It is revealed that all the tractors under study have different reliability and different rational service life.