Methanol synthesis from sustainable feedstocks will play an important role in the future's energy system. To enable an accurate design of crude methanol distillation systems, detailed knowledge about the amounts of side products in crude methanol is required. In this study, crude methanol samples obtained from four experimental setups covering a wide range of process conditions were analyzed for their main and side compounds. By means of a Spearman correlation analysis, the amount of carbon oxides in the reactor feed was identified as determining for the formation of side products. Trend lines describing the amount of side products were derived from the experimental data to enable studies on the downstream treatment of crude methanol.