The mass content of soot (C) in the cylinder of a tractor diesel engine (TDE) is directly affected by the temperature conditions, the excess air coefficient, and the chemical composition of the fuel. Methanol (M) does not form C particles during combustion. As the C chain in the fuel molecule increases, the propensity to C formation during combustion increases. However, in the presence of oxygen atoms in the initial fuel molecule, it significantly slows down the rate of nucleation of primary particles. During the evolution of the particle in the cylinder of a TDE when working on rapeseed oil methyl ether and methanol (ROMEM), a number of characteristic stages are identified.