How Long Does Diesel Last With Stabilizer?

How long diesel fuel will last depends on various factors, like the storage method and the ambient temperature. High-quality diesel fuel will stay fresh for a year if stored under ideal conditions. The "ideal conditions" refer to diesel fuel stored in an airtight, sealed container in a cool, dry place, preferably around 70°F or 21°C.

Since we don't live in constantly ideal weather, diesel fuel needs additives or stabilizers if you need to maintain its freshness for extended periods. All hydrocarbon-based fuels will begin oxidizing under prolonged storage, and with diesel, this can create harmful deposits that can clog or damage the injectors, fuel lines, valves, and other internal components.

Moreover, storing diesel in a tank or container attracts unwanted moisture or water, creating a breeding ground for mold, fungi, and bacteria, also called "diesel bugs" or diesel algae. It doesn't take much for diesel to absorb water from the air and its surroundings, and those "diesel bugs" or microbial sludge could also clog the filters and fuel lines.

The average auto shop or online retailer will have a selection of diesel stabilizers to prolong the life of diesel fuel. For instance, the E-ZOIL STORZALL is a fuel stabilizer suitable for gasoline, diesel, and biodiesel fuel. It utilizes an anti-oxidant formula that stabilizes fuel, prevents degradation, and keeps diesel fresh for up to 12 months.
The product is safe for all gasoline and diesel engines — including common-rail direct-injected (CRDI) or direct injection mills — and is suitable for cars, trucks, boats, commercial or industrial machinery, boats, or stationary engines. Pouring a single 16-ounce bottle of E-ZOIL STORZALL can treat 200 gallons of fuel. 

Meanwhile, diesel stabilizers like the Sta-Bil Diesel Formula claim to protect diesel fuel from moisture and degradation for up to 24 months with the correct dosage. It's also great for every fill up to deliver year-round protection from moisture, sludge, and sediments. Sta-Bil recommends pouring 30 ml of the product for every 38 liters (ten gallons) to protect the entire fuel system. But when storing diesel, pouring 30 ml for every 19 liters (5 gallons) will keep the fuel fresh.

We mentioned earlier that fresh diesel will stay fresh for six to 12 months with proper storage, but here's the catch: untreated diesel will start degrading or oxidizing within a few months in storage, but it depends on the fuel quality.

Most diesel fuels will begin degrading within 28 days of storage. Moreover, B5 biodiesel is good for up to a year with proper storage, while B20 will stay fresh for eight to twelve months if treated with anti-oxidants or additives. Unless you have prepared a climate-controlled garage and some airtight containers, treating diesel fuel with stabilizers will help extend its lifespan without affecting its quality. In addition, using a diesel stabilizer is easier and more cost-effective than regularly draining your storage tanks or containers.

The most suitable container for storing diesel fuel is a container or storage tank made of aluminum, fiberglass, or steel. Alternatively, a commercially available Type I container or Type II safety can that meets Occupational Safety and Health Administration (OSHA) requirements for flammable liquid storage is ideal. In addition, OSHA has approved polyethylene plastic oil drums for storing flammable liquids like gasoline or diesel. Lastly, it's best to avoid storing diesel in containers that contain or are made of copper, lead, brass, or tin to avoid premature oxidation of the fuel.