The maximum heat of combustion rapseed oils (high- and low eruck asid containing ) and as soya oil and methyl ethers of their fat acids it was determined in a calorimeter of burning with bomb B-08МА. On iodic number, number омыления and fat asid structure above-named biofuel, the maximum (lowest) heat of combustion was calculated. The error of calculation of heat of combustion makes from-70 up to +120 кJ/kg at the common level of 40.000кJ/kg. Heat of combustion hidh eruck oil on 1,5-1,6 % is higher than heat of combustion low eruck oil.