Diesel fuel can be thinned with gasoline or kerosene if desired which always works and the percentages are easy to ask for at a bulk fuel dealers office or the APA.org home page- the fuel dealer will be faster.
The even better option is to purchase a Racor 1100 model centrifugal fuel filter it separates the water and dirt with its patented centrfugal filter system.
The model 1100 unit can be purchased with a 12 volt heating element installed to keep the fuel warm at all times to make it your tractor happy.
The diesel fuel can be treated with "Heat" fuel conditioner or Seafoam to keep it happy as well.
You should try to keep the can or cans off the floor of the garage, barn, etc., during the winter and spring months.
You can safely dilute the diesel fuel with kerosene and use the Racor filter which will remove water and debris down to 5 micron but you cannot use gasoline as a diluting liquid as it will eat the plastic drain bowl.
The clear drain bowl will allow you to drain the water and dirt from the fuel every day with no worries about water or dirt and ice in the fuel if you purchase a Racor filter unit with thermostat controlled fuel heater. (it does not draw a lot of amperage when heating fuel for you).
I can tell you from personal experience they are an excellent fuel filter and will be worth every penny in the piece of mind department especially when working in the winter months.