Water contamination is a common problem. Condensation contaminates diesel fuel and allows microbial growth. Microbial growth feeds on the diesel fuel but lives in the water. High sulfur diesel fuel once killed this growth. Today's low sulfur fuels don't. Biocides will kill the microbes. But then, deceased microbes settle to the bottom of the tank, along with rust and dirt -- each contaminate potentially the cause of plugged filters and injectors. Eliminate the water, and you eliminate fuel problems.
Read more: https://www.dtnpf.com/agriculture/web/ag/equipment/article/2021/06/14/high-quality-diesel-increases-power