Over the years I have owned and worked on a lot of used equipment that folks weren't very careful with there fueling practices. Have removed a lot of tanks over the years for cleaning. I won't think about removing a cap on a piece of equipment without blowing compress air around the filler cap first. I have a compressor on my fuel trailer and a air hose hanging by my fuel tanks at my buildings. If I am fueling out in the field with the fuel trailer I even put a rag around the fuel inlet with the nozzle. I came from the buy clean fuel and keep it clean school. A buddy is not very careful with his fueling practices and it cost him twenty grand last fall to get his late model combine back up and running. He now has rethought his refueling practices. These newer diesels don't like dirt and water.