Expediency and efficiency of use of natural gas motor fuel (GMF) for mobile agricultural machinery is defined on the basis of alternative calculations of commercial effectiveness of use of the compressed natural gas (CNG), liquefied natural gas (LNG) and the liquefied petroleum gas (LPG) in large agricultural enterprise «Kazminskoye» in the Stavropol Territory where costs of fuel for machines and tractors make 222.5 million rubles a year. Need of field gas refueling of tractors and combines as a specifics fuel utilization by mobile agricultural machinery was considered at calculations. For an assessment of a type of GMF and influence of cost of a refueling complex on commercial effectiveness the authors have carried out comparative calculations of technical and economic efficiency of utilization of CNG, LNG and LPG, taking into account and without a refueling complex. High efficiency of GMF utilization was showed: fuel costs decrease by 1.7 times, the payback period of capital investments equals to 0.4-4.2 years. The best results were obtained when utilization LPG. Total costs of re-equipment and a refueling complex in option with LPG are 3.5 times as less as with CNG, and 6 times as less as with LNG. The payback period of capital investments for re-equipment without refueling complex equals to 0.4; 0.8 and 2.4 years respectively for LPG, CNG and LNG. Taking into account refueling means it increases to 0.9; 2.4 and 4.2 years. In 10 years the net present value taking into account refueling means equals to 276.7 million; 289.9 million and 206.8 million rubles for LPG, CNG and LNG respectively due to fleet re-equipment.