300L diesel in our starboard tank were contaminated with dirt and water. After two years of refueling while adding anti Diesel bug additives, we had the choice to fuel polish (which is a filtering and water separation process) or pump out all fuel, clean the tank and replace it with fresh diesel.
‘Slick Hull’ pumped the tank out (company in Portimao) and cleaned it. We had 3 hour express service.
Afterwards we filled with initial 60L of fresh diesel and completed the rest at the boat gas station. Interesting the tank gauge showed still empty even when you could see 60L of Diesel swapping around of the tank bottom 🙂