Unlike a car or truck diesel fuel sits in some tanks for years, because it is stored for emergencies not regular use.
Consider these numbers. A generator you want 24 hours of run time. At full load you burn 20 gallons per hour so, you need 480 gallons in the tank for every 24 hours you want to have power. If you test your generator once a month for 15 minutes, you will use 7 gallons per hour or 3 hours per year for a total of 21 gallons per year. So, without a major power outage, you would not use all your fuel for 8 years.
Let us assume you refuel every other year and add 50 gallons. You still have 430 gallons of the original fuel in the tank. This fuel is now 24 month old. Adding new fuel does nothing but gets you a full tank with 480 gallons of old fuel.
Fuel must be “Clear and Bright” and to ASTM D975 standards to comply with NFPA 110, Standard for Emergency and Standby Power Systems Code. This standard covers performance requirements for emergency and standby power systems.
After 90 days fuel discolors and solids form. Fuel is no longer clear and bright.
What is your plan to deal with the problem?
Hope is not a plan.