Preparing your diesel-powered equipment for winter's arrival is an important task. If your engine will be sitting idle for several months, such as a boat that's been hauled out for winter storage or farm/construction machinery which will not be used again until spring, you must winterize the fuel. It's any easy task to perform and not terribly expensive.
If your fuel tank is less than full, fill it with the freshest fuel available. Buy it from any dealer who sells large quantities such as a truck stop like Petro or Flying J. These places sell thousands of gallons of diesel fuel daily and are always receiving deliveries of fresh fuel to replenish their stocks. Fill a jerry can or two and top off your tank. If your boat is still afloat, take special care not to spill any fuel into the water.
Unlike some petroleum distillates, all diesel fuel contains a small amount of water. In the boundary area formed when the water and fuel separate, algae and bacteria begin to grow and multiply. When they die, they fall to the bottom of your fuel tank. Over time, this buildup creates sediments which can clog the fuel filters/injectors and eventually do serious damage to your engine. Adding a biocide kills the algae/bacteria and prevents their regrowth. Fuel stabilizers help prevent the paraffins in diesel fuel from separating and creating sludge.
EPA-mandated ultra-low sulfur diesel has different chemical properties than the older formulations it replaced. The low sulfur content causes the fuel to begin to gel at higher temperatures. Many refineries change their winter diesel blends to partially overcome this. But you should perform some prudent actions as well.
Top off your fuel tank as frequently as possible. Fresher fuel has less of a tendency to gel at lower winter temperatures.
Consider adding a diesel fuel additive/conditioner. Some of these products contain a biocide as well. Check with your car dealer or service shop. They may recommend a specific brand based upon your engine's manufacture or the specific winter weather conditions where you live.
