The subject of the research is to determine the parameters of the diesel intake and gas exchange pro-cess when using a mixed fuel (MF), consisting of diesel fuel (DF) and rapeseed oil (RO). The main goal of this work is to determine the dependences of the parameters of the intake and gas exchange of a diesel engine on the composition used by the MF. To achieve this goal, theoretical and experimental studies of the D-245,5S tractor diesel engine with a characteristic of 4ChN 11,0/12,5 were carried out on the following MF compositions: DF – 80 % + RO – 20 %, DF – 45 % + RO – 55 %, DF – 20 % + RO – 80 %, as well as pure diesel fuel. During the carried out studies there were obtained the dependences of the hourly air flow rate, the cylinder filling factor and the charge density in the intake manifold of a diesel engine when operating on DF and MF on the crankshaft rotation speed and load at = 1800 min–1 and = 1400 min–1. It is theoretically determined and experimentally confirmed that the composition of the used MF has practically no effect on the characteristics G_в, η_v and ρ_к depending on p_e of the diesel engine. As a result, it was found that with an increase of n from 1400 to 1800 min–1 on all compositions of MF the G_в increased from 276 to 394 kg/h, from 1,44 to 1,70 kg/m3, and at increase of n from 1800 to 2000 min–1, the G_в decreased from 394 to 322 kg/h, from 1,70 to 1,49 kg/m3 and from 0,97 to 0,77. With an increase p_e from 0,2 to 1,2 MPa on all compositions the MF increased, at n = 1400 min–1, from 187 to 276 kg/h, ρ_к from 1,29 to 1,44 kg/m3 and η_v from 0,73 to 0,97, at n = 1800 min–1, G_в from 274 to 394 kg/h, ρ_к from 1,29 to 1,69 kg/m3 и η_v from 0,83 to 0,91, respectively.