We have established the effect of production temperature conditions on the performance characteristics of the composite additive Evropris for diesel fuels, including cetane-booster, pour-point depressant, antiwear, smoke-suppressant, and dispersant components. We determined the optimal temperature for mixing the individual components of the additive that ensures maximum improvement in the cetane number and anti-wear properties of the diesel fuel and reduced exhaust smoke. The composite additive improves the properties of the fuel as a result of the synergistic effect between its components. We use a semi-empirical quantum chemical method to estimate the excitation energy for the individual components of the additive to be excited to the lower triplet state plus their stability.