At the end of summer, Andris purchased two tons of necessary fuel. Shortly after that, the tractors and combine harvester began to show technical problems. Andris urgently contacted mechanics. After several repairs, including replacing fuel filters, the farmer resumed work. However, it was only for a short time. After consulting with more experienced specialists, the main hypothesis for the cause of the malfunctions was proposed to be poor-quality fuel. At the end of summer, Andris bought two tons of diesel from the company *Straujupīte*. Before contacting the supplier, the farmer sent the fuel for testing. According to the analysis results, the permissible level of impurities in Andris's sample was found to be about three times higher than the norm. The farmer contacted the fuel supplier, but the company rejected all claims, emphasizing that the client likely stored the fuel incorrectly, which was intended for machinery.