This past fall, when I got my delivery of home heating oil, the drivers next stop was a farm diesel fuel delivery. More problems are created with improper storage on the end users end than on the delivery end. If you have a tank that is vented to the atmosphere and don't keep it full, condensation will form on the inside in the hot muggy days of summer. This isn't a problem for the oil dealers because they turn over enough product and they also test their tanks for water on a regular basis. Do you know when the last time your home heating oil was tested for water? I check mine on a regular basis and remove any water before it becomes a problem for me. In twenty years, that was only one time and it was a result of not keeping the tank full during the summer months.