Does Diesel Go Bad?

September 19, 2022

Does Diesel Go Bad?

Vehicles that run on diesel instead of gasoline may not be as common in the United States as they are in Europe, but vehicles that require power over speed need it. Some personal vehicles and many pieces of mechanical equipment, such as lawn mowers and generators, use diesel to operate. This might tempt users of diesel engines to stock the fuel for future use.

It is well-known that gasoline expires, but does diesel go bad in storage?

Diesel does stay fresh longer than gas, and with the right practices, can last in storage for years. Taking good care of diesel fuel can extend its life and keep it pure. This takes a little knowledge and watchfulness, but can preserve the life of your engines as well as your fuel.

What Can Make Diesel Go Bad?

Diesel fuel is a chemical, so it is subject to chemical reactions that we often take for granted in everyday life. How and where you store your diesel can influence the amount of time it takes for the fuel to go bad. Everything depends on what elements the diesel is exposed to. All four material states have adverse effects on unprotected diesel, making it react in ways unfavorable to its reuse. 

  • Heating anything causes chemical reactions that we are all familiar with, such as cooking or boiling of water. Being subjected to heat also causes diesel to break down and burn. Diesel used in an engine is subjected to high pressure that makes it combust, fueling the mechanical activity. Diesel subjected to very high temperatures can also combust, but simply leaving diesel out in the summer heat can have adverse effects. Diesel evaporates and also forms condensation. Keeping diesel in a cool area of 70 degrees or less can extend the life of stored diesel.
  • Water and condensation are not only bad for diesel on their own, but bring many other hazards that can shorten the life of diesel that has been stored. Diesel left out in heat over 70 degrees can form condensation, which dilutes the fuel. Watered-down fuel can damage your engine as well as bring rust and fungus into delicate parts such as fuel injectors. 
  • Bacterial and fungal growth can take place in your fuel if it is not properly stored or very old. This is the unfortunate effect of both water invasion and condensation, and can result in sludge and goo building up in your diesel fuel. Fungus and algae grow in diesel affected by condensation because it is warm and damp, where such plants thrive. Bacteria and microbial growth can also become very active when diesel is improperly stored and not looked after.
  • Oxidation is a chemical reaction with the element oxygen, which is a gas that most life forms need to breathe in order to survive. Since it is found everywhere in our atmosphere, it is important to ensure that there isn’t any in diesel fuel. When diesel is affected by oxidation, it breaks down and becomes less pure. Gooey sediment forms, which can damage your engine.
  • Other acid-base reactions can also degrade diesel. Contact with certain metals such as copper or zinc can mix with your diesel and speed up its degradation. Any fuel storage should be kept away from other chemicals and compounds, such as cleaning fluids, swimming pool chemicals, or lawn fertilizer because any of these can start reactions that degrade your fuel.
Does Diesel Go Bad

How Can You Tell if Diesel Has Gone Bad?

Fuel that has gone bad is detrimental for your engine. A vehicle’s engine is a collection of very fine moving parts that will not operate properly if they are clogged or sticky. Having bad fuel run through the engine can cause it excessive wear and tear, and diesel fuel is n o exception. Sludge from bad fuel can even ruin the engine.

If your engine is idling roughly or slow to accelerate, this can be a sign that the diesel fuel in your tank has been compromised by some impurity. Before you start the engine, consider how long the diesel has been in your tank or container.

There are a few preventative signs that indicate your diesel has degraded. If you haven’t started the engine in a while or are storing diesel, a cautious approach would be to check for these signs.

  • Microbes and oxidation can cause a foul smell in your diesel fuel.
  • Algae, fungus and condensation can cause gel and sludge to appear in your container.
  • Your fuel is cloudy or dark in color.
  • There is film on the surface of the fuel.
  • There is debris or sediment in the container.
  • Your engine is emitting black smoke.
  • You are getting less fuel efficiency from your tank.
Does Diesel Go Bad

Safely Storing Diesel

How do you store diesel safely and prevent degradation? There are a few things you can do to prolong the life of your stored fuel. Diesel that is well stored can last almost two years, while diesel that is degrading only lasts about six months. Keeping diesel stored safely and keeping outside elements from turning it sour are both byproducts of each other, meaning you get twice the return for a small amount of effort.

Containment

The container you store diesel in can make a lot of difference in how long your diesel lasts. It is very important that diesel is stored in a container meant for the purpose. Some people try to recycle items such as milk jugs or large soda bottles to store extra fuel in, but these containers are not made of material that is safe for storing fuel. Even if clean and sanitized, everyday bottles are subject to chemical reactions that could cause them to leak or melt. Be certain that all of your fuel storage was made for storing fuel.

Plastic vs Metal Containers 

When choosing between plastic and metal fuel storage, there are a few considerations that will help you decide which you prefer. Both have benefits and drawbacks. 

Plastic containers might expand when full, especially in heat. They may also leak or become porous if diesel is stored long term. When plastic containers expand, it weakens the integrity of it and allows leakage. Plastic is also vulnerable to warping when exposed to sunlight for too long, as well as when the diesel expands under pressure. However, many fuel-rated plastic containers are inexpensive and perfect for short-term storage of a few gallons each.

Metal containers might seem like the way to go, and for long term storage they are preferable. However, metal canisters and barrels also have drawbacks that should be taken into account. Metal rusts, and this compromises its structural integrity. Water pooling on the floor or on the lid of a metal container can accelerate the process and open your fuel to seepage, water, and contamination. In extreme circumstances such as exposure to fire, metal might explode, creating shrapnel.

Legal Considerations

Some municipalities have guidelines and restrictions on how much fuel you can store or where you can store it. Check with your town, county, and state for any such guidelines before you try to store any diesel on your own.

In some places there is a limit to the amount you can store in one container or how large a single container can be. Some cities and counties will only allow storage of a certain total amount, no matter how many containers it is in. Depending on how the property is zoned, or permitting considerations such as local water tables, it may be illegal to have an in-ground tank, especially on residential property. Residents may also be prohibited from storing fuel in a building people dwell in.

How Much Diesel Should You Store?

With fuel prices so high, it may be tempting to keep a lot of fuel stored for future use. If you are careful with your fuel, this could be a good strategy. However, it is important to remember to keep an eye on your diesel fuel’s integrity and make sure it has not become contaminated. A lapse in watchfulness could become a loss of your hard-earned money.

With that in mind, you should only store enough diesel to last at most two years. Suggested methods of protecting your diesel would include examining your use and considering a few factors.

  • Store your diesel in containers according to your needs. If you use a lot of diesel, such as if you run a small business, drive a semi, or have an agricultural interest, you may need a drum or even a tank for your diesel. If you are a homeowner, boater, or other private user, a tank might be an unsustainable expense and a drum might spoil before you can use it all. Separate, smaller containers may be a better option for home and personal use.
  • If you have multiple containers, it is best to use the oldest fuel first and stagger your purchases so that you always have diesel that is fresh. 
  • If you plan on storing diesel long term, there are treatments you can add to prevent common issues such as water contamination, oxidation and biome growth, including algae, bacteria, and film.
Does Diesel Go Bad

What if Diesel Has Gone Bad?

If your diesel is showing signs of spoiling, don’t give up hope. If you are willing to invest in your diesel, you can salvage some or all of it. The more diesel you have, the more effort and expense is involved, so it is important to consider whether it is worth the expense.

Additives such as diesel fuel stabilizers, biocides, and water absorbers can help diesel last even after it’s been contaminated. None of these can replace monitoring and taking care of your diesel beforehand, but it can help mitigate loss if your diesel goes bad. Water absorbers attract water molecules into clumps. Stabilizers can neutralize most other chemical reactions, such as acid-base reactions. Biocides will kill most bacteria, algae, fungus and film.

If you are able to successfully treat your contaminated diesel, the next step is to filter it. Diesel fuel filters can help remove any sediment or sludge, as well as any water or condensation. This is not a perfect fix, though, and should only be used in emergencies or when the fuel has limited contamination.

In the event your fuel has gone bad and cannot be salvaged or filtered, it is important to remember that diesel is a chemical and can contribute to pollution. Dispose of your spoiled diesel as you would any hazardous waste. Otherwise, it could seep into the ground and be ingested by plants, animals, and other humans.

The Life of Your Diesel Fuel

Diesel may go bad in up to six months, but that’s only if it is not monitored and treated. When diesel is properly taken care of, it can last up to two years. Whether you use diesel for transportation, business, maintenance, or recreation, taking care of stored diesel can not only save you money but can also preserve the integrity of the engines you use.