The durability and reliability of mechanical gear transmissions, which also include spiroid gears, depend significantly on, among other factors, the lubrication parameters of the transmission. This type of transmissions is currently used in the drive systems of various types of vehicles. Under high loads, the aforementioned gear transmissions exhibit increased contact pressures on the meshing tooth surfaces. This results in the lubricant being "squeezed" out of the working space between the teeth, thereby increasing friction. This undesirable effect can be eliminated by generating an elastohydrodynamic (EHD) oil film in the working space between the meshing gear teeth. To determine the minimum oil film thickness, the isothermal model developed by Dowson is used, where the oil viscosity is given at ambient temperature and pressure. In reality, the oil temperature during gear operation deviates from the assumptions made in Dowson’s model. In view of the above, in order to account for real operating conditions in the oil film, oil film thickness correction factors are used that consider the effect of temperature on oil viscosity. Accurate determination of the value of the oil film thickness correction factor is a complex issue; therefore, with the aim of providing the best possible approximation of the actual operating conditions of a spiroid gear, the authors proposed a new approach to this problem. The developed method utilizes oil characteristics, with properties such as viscosity and density determined experimentally. The gear operating parameters were determined by assuming oil temperature as a prescribed value in the computational model, corresponding to the actual temperature occurring in the meshing parts of the gear: the disc wheel and the worm. The computational model used to determine the oil film thickness also accounts for the materials used, the load-carrying capacity of the oil film and the oil flow velocity. The developed method is universal and can also be implemented for calculating other types of gear transmissions.