In this work, the reliability of the KamAZ-4308 truck frame is increased, taking into account its maintenance frequency. This brand was chosen due to the fact that it is one of the best-selling cars in Russia among the cars with a gross weight of 14 to 40 tons in 2019. A method for optimizing the value of the intervals between the planned car maintenance (MAINT) is proposed. When calculating the reliability, the problem of minimizing the amount of initial data was solved in order to reduce the experiment time, its labor intensity and the financial testing costs. As one of the options for reducing unit costs, a change in the material for manufacturing a truck frame is considered. The empirical and approximating functions of the general totality of the finite volume (GTFV) of the Tp frame of the KamAZ-4308 car service life are obtained. At a given failure rate λ = 10-7 h-1, period values τ = 10 h and cost U/C = 100 the optimal frequency of maintenance is Topt = 993 h ≈ 1,4 month taking into account the minimum technogenic risk Smin = 0,0513.