This is in response to two posts concerning fuel. One person was having a problem with a fuel system restriction that re-occured. The second post was about refueling once per year. I'm sure you folks are aware of a diesel fuel systems return fuel route sending hot fuel back to the tank. This causes the tank to sweat (condensate) on the inside walls putting water in the tank. A form of algae grows in diesel tanks that contain water. As the algae grows it comes loose and gets into the fuel system. A biocide will kill the algae bloom but the tank must must be cleaned. The algae feels like a slim that can be felt on the filter paper. You don't see this very often, but keeping your tank full displaces the air and prevents algae from getting started. Hope this is helpful. Fred