In this paper, the numerical simulation of the diesel and gasoline fuels injection in a constant volume chamber and in a cylinder under the operating conditions of a compression ignition (CI) engine is conducted. The simulation results are compared with the experimental data which derived from fast imaging techniques. In order to check out the possibility of using gasoline instead of diesel to increase the volumetric efficiency of the CI engine, the spray characteristics of the gasoline and diesel with injection pressures of 40 and 80 MPa, as well as temperatures of 243, 273 and 313 K, under cold start condition is investigated. The results show that under the same conditions, the vapor penetration length for the two fuels is approximately equal and due to the lower volatility of the diesel fuel, its liquid penetration length in 40 and 80 MPa injection pressures was found to be 7 and 9 mm higher than gasoline, respectively. In addition, the reduction in fuel temperature from 313 K to 243 K leads an increase in the penetration of gasoline and diesel liquids by 12 and 10 mm, respectively. Finally, the decrease in the evaporation rate causes a non-homogeneous mixture and results an increase in the unburned hydrocarbons and emissions.