Is it OK to Use Old Diesel? Understanding Diesel Degradation and Its Effects

October 3, 2023

Is it ok to use old diesel?

Diesel for generators and bulk tanks can be stored safely for 6-12 months. It is sometimes needed in emergencies. Hence with proper care and precaution, it can even be stored for over a year. Exposure to heat, air, and water are the main factors that can affect the shelf life of diesel.

It is very important to store diesel with proper measures as old diesel clogs machinery. Many conditions are important for preventing diesel from being contaminated. Learn if it's ok to use old diesel and the many factors regarding expired diesel by reading below.

ok to use old diesel

How is unused diesel affected over time?

Diesel can be easily contaminated from its supply chain to the storage tanks that It is stored in. Hence old diesel has the highest chance of having the following issues present in it:

  1. Hydrolysis or Water Condensation: when diesel gets in contact with water, causing condensation on the top of the tank, it will lead to droplets of water falling into the diesel, encouraging bacterial growth.
  2. Microbial Growth: this is caused by the presence of water in the tank, usually caused by condensation—bacterial growth, like algae, forms which produce an acid that clogs the tank.
  3. Oxidation: this happens when diesel is exposed to oxygen. It causes diesel to thicken into a gummy and sludge-like form which can clog your machine's filters.

Old diesel may show the following signs if it has gone bad:

  • Gummy, sludge-like texture.
  • Hard to start your generator since it does not run through the pipes smoothly.
  • Give out black smoke as it does not burn properly due to becoming tarnished.
  • It has a rotten smell.

What are the issues with using old diesel?

Using old diesel for generators and bulk tanks is the worst thing that can be done to them. Make sure to keep your generators checked as old diesel tends to stick to the pipes of the machinery, causing the machine to break down sooner if not later. 

Bulk Tanks should also be clean and dry before storing diesel to prevent contamination to get the best out of your fuel.

It would be helpful if you keep a check for signs of old diesel and use Water absorbers, Stabilisers, and biocides that help in cleaning diesel to prevent your machines and tanks from wearing out. 

You can get fuel delivered easily for your generators with our nationwide generator refueling service.

What is fuel polishing, and how does it help?

Suppose your fuel is not treated regularly and has fungi or algae buildup. Then comes the concept of fuel polishing. It removes any contamination from hydrolysis, bacterial growth, to oxidation from diesel; it can be done by running your diesel through several filters from one tank to another. 

Our Top Questions Regarding If it's ok to Use Old Diesel

How long does diesel last before it goes bad?

Diesel can be used for 6-12 months if stored properly. It is important to store it in a cool and clean environment without contact with water. 

Can you use 10-year-old diesel?

No, you can not use old diesel as it will form a sludge-like texture till then and clog up your machinery hence ruining it. Hence 10-year-old diesel should be immediately disposed of.

Is it safe to use 5-year-old diesel?

No, diesel should not be used after five years. Diesel that is kept in proper conditions can only be used within a 6-12 months period.

Is diesel OK after two years?

No, it is not ok to use old diesel after two years of storage as it will have a gummy consistency causing your machinery to break down. Hence only use diesel that is stored for a year.

How can we prevent diesel from being contaminated?

Tanks should be cleaned properly before putting diesel in them. They should be stored in a cool and dry place. Humid and warm places should be avoided. You can also use water absorbers, stabilisers, and biocides that help prevent diesel from being contaminated.

Access faultless fuel with Fuel Logic

It is very important to store diesel in optimal condition to improve its shelf life to a year. As of now, we know the adverse effects of using old diesel for generators and bulk tanks. Now you know if it's ok to use old diesel – You must assess the length of time stored on a case by case basis.

It will clog the filters of generators and cause corrosion. Not keeping clean bulk tanks will spoil the new diesel you store in them as soon as possible. Hence, it is very important to check signs of any spoilage, such as black smoke, rotten smell, and gel-like consistency to prevent wear and tear.

If you want to get diesel delivered safely, it is just one click away with our on-site fuel delivery service.

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