The article is devoted to the application of methanol-fuel emulsion as alternative motor fuel in the 4Ch 11.0/12.5 tractor diesel engine. The maximum concentration of methanol in the emulsion is determined; it should not exceed 25% to prevent the uneven diesel engine operation and misfiring in the cylinder. According to the study results of stability and the primary tests of engine, the optimal composition of methanol-fuel emulsion is accepted for 4Ch 11.0/12.5 tractor diesel engine: 25% of methanol, 0.5% of S-5A succinimide, 7% of water, 67.5% of diesel fuel. The results of experimental studies of influence of methanol-fuel emulsion on the indices of combustion process and the characteristics of heat emission of the 4Ch 11.0/12.5 diesel engine are given. In order to determine and optimize the main parameters of diesel engine operation on methanol-fuel emulsion, the bench tests including the full range of regulating, loading and speed characteristics were carried out. The values of combustion process indices and heat emission characteristics of diesel engine operating under nominal mode are determined: the maximum temperature of the cycle increases by 16.2% and equals to 2580 K; the maximum pressure increases by 0.4% and equals to 8.54 MPa; the severity of the combustion process increases by 74.5% and equals to 1.251 MPa/degree; the angle corresponding to the ignition delay period increases by 36.4% and equals to 30 degrees of crank angle change; the heat emission speed increases by 2 times and equals to 0.177; the heat emission value at maximum temperature increases by 12.6% and equals to 0.789; the heat emission value at maximum pressure increases by 14.7% and equals to 0.688.