"Dimethyl ether (DME) is a clean fuel with a high cetane number and soot-free combustion, making it a suitable substitute for fossil fuels. However, optimizing the direct DME synthesis process from syngas (STD) requires a deep understanding of equilibrium limitations and the interaction of operating conditions. In this study, with the aim of determining the optimal thermodynamic conditions as well as evaluating the final product quality from a combustion perspective, the equilibrium of the STD process was analyzed using the Gibbs free energy minimization method. Calculations were performed using Aspen Plus software and the Peng‑Robinson equation of state over a temperature range of 100 to 500 °C, a pressure range of 1 to 50 bar, H₂/CO molar ratios from 0.5 to 4, and CO₂/CO ratios from 0 to 2. The effects of adding steam and inert gas (N₂) on conversion and selectivity were also evaluated. All calculations were based on the assumption of single‑phase gas equilibrium. At 250 °C and 40 bar, CO conversion reached about 95% and DME selectivity exceeded 92%. Increasing the temperature to 500 °C reduced DME selectivity to below 70% and increased CO₂ selectivity to above 30%. Adding 20% steam to the feed increased hydrogen production by up to 20% but decreased DME selectivity by about 12%. In contrast, adding excess CO₂ reduced DME selectivity without significantly changing hydrogen conversion. Comparison of the direct and indirect routes showed that CO conversion in the direct route exceeds 95%, while in the indirect route it remains below 50%."