Solubility of biodiesel fuel components in fossil diesel fuel–methanol–rapeseed oil methyl ester, fossil diesel fuel–ethanol–rapeseed oil methyl ester and fossil diesel fuel–ethanol–rapeseed oil ethyl ester systems was investigated. The solubility of components in the fossil diesel fuel–ethanol–rapeseed oil methyl ester system at 20 °C was substantially higher than in the fossil diesel fuel–methanol–rapeseed oil methyl ester system. The solubility of components in the fossil diesel fuel–ethanol–rapeseed oil ethyl ester system was slightly lower than in the fossil diesel fuel–ethanol–rapeseed oil methyl ester mixture. The moisture content of ethanol had a great influence on mixture solubility. With decrease of temperature, the solubility of components in the fossil diesel fuel–ethanol–rapeseed oil methyl ester system decreased.