The development of the market of second-hand equipment causes the expediency of its use in farms with small seasonal loading of harvesters as at high technical readiness of combine harvesters and low seasonal loading costs of their attraction increase. However, with the increase in the area of harvesting at low reliability of cars and big expens-es of time for the elimination of consequences of technical refusals of the enterprise incur losses from lesions in production because of violation of agrotechnical terms. In modern conditions justifica-tion of a rational idle time of grain-harvesting cars for the elimination of consequences of technical refusals taking into account their seasonal loading and the major production and natural factors is re-quired. Economic-mathematical modeling defined rational indicators of coefficient of idle time at vari-ous seasonal load of a combine harvester of the 3-rd class. It was established that with the reduction of seasonal loading of a combine harvester of the 3-rd class with 300 the coefficient of idle time in-creases to 200 hectares with 0.2 to 0.8. At the ra-tional indicator of coefficient of idle time equal 0.4, the rational time between failures makes nine hours and the time of delivery of spare parts is two hours. The increase in agrotechnical terms of cleaning due to the use of cultures, grades, various on precocity, allows lowering requirements to reliability. The greatest complexity of elimination of the conse-quences of technical failure have threshing and separating device, and the maximum monetary costs are necessary for the repair of motor-propulsion of the harvester. Industrial implementa-tion of research results in coordination of efficient ratio of idle time to eliminate the consequences of technological failures and seasonal loading of combine harvester of the 3-rd class allowed us ob-taining annual economic benefits of up to 740 rub. / hectare.