Can Diesel Go Bad? [And How Long Does It Last?]

With the continuing rise of fuel prices (gas and diesel), have you ever thought of stocking up on diesel for future use to save a few bucks, but wondered des it go bad? Well, this article is specifically made for you. We have researched the same question, and this is what we have found. 

Yes, diesel does indeed go bad, especially without fuel additives. It can go bad as quickly as 30 days. But this depends on the conditions upon which the diesel is stored. With additives, fuel can last six to 12 months if stored around 70 degrees F, more than 12 months if stored below 70 degrees F.

Interested to learn more about diesel going bad? Continue reading as we discuss other related questions that may help you solve your curiosity about the topic, such as proper storing, reconditioning old diesel, cleaning dirty diesel, and more. We will also be suggesting interesting articles at the end of this write-up to satisfy your cravings for knowledge.

Diesel engine refueling, Can Diesel Go Bad? - And How Long Does It Last?

Does diesel expire?

Diesel and gasoline are both synthesized and refined oil designed to be used for running combustion engines. Both of these fuel sources have a shell life. This means that there is only a certain period that is good to be used.

Once it expires, you should not consume it. For diesel to last, it should be properly stored, preferably at a cold temperature for it to last you more than a year in storage. 

If you are planning to do so, make sure that it is protected from the elements such as heat, as it is one of the worse things that can happen to your diesel. 

Diesel Fuel at gas station

Condensation has also been one of the main culprits in turning a diesel bad. This is the result of diesel being stored in a hot place because diesel evaporates since it is liquid. It then condensates and turns into water, thus resulting in them being together.

This damages the integrity of the diesel because, at this point, it is not pure diesel. When you put it inside the tank of your car, the mixed water can cause rust and algae to grow. 

That is why it is imperative to store diesel in a relatively cool place. The cold will derail the process of evaporation and avoid the formation of water. 

How can you tell if diesel has gone bad?

Refilling gas in gas station

There are multiple tell-tale signs that the diesel fuel has gone bad. Sadly, some signs would only be observed if you have already pumped the bad diesel fuel inside your car. That is why you should be very careful when pumping your fuel.

If you feel that the gas station that you are trying to refuel from is a bit sketchy, then it is better to be safe than sorry. We suggest that you get fuel in reputable gas stations. 

Sometimes we can be fooled by choosing a station that sells cheaper gas, unknowingly that the fuel they are selling is not pure and is already mixed with water. We might've saved a few bucks in gassing up, but this can cause major problems in your vehicle that can reach thousands of dollars for repair.

Getting dirty diesel fuel inside your car is havoc on your internal combustion. Unwanted objects like sludge and varnish can get into places like your injector fuels and some parts of your engine. This will clog your injector filters and leave deposits that can greatly diminish the efficiency of your car's motor.

You can also expect to get lower fuel mileage than usual. The engine might feel like it is hesitating or not giving enough power when accelerating and rough idling can also be expected.

What to do if you accidentally put bad diesel in your car?

As we have established, expired or bad diesel fuel can cause damage to your vehicle. So getting some inside your fuel tank could mean a world of trouble for your vehicle.

When this happens, you should immediately take action. If you suspect that what's in your tank is bad diesel, immediately have it checked by a trusted mechanic. In this type of situation, the sooner it is treated, the better.

Having this type of repair done can cost you anywhere between $400 to $1,500. It is worth noting that prices may vary depending on your location and the severity of the damage (if any) inflicted.

Always remember that your engine is the reason why your car is running, and it uses fuel to power itself up. Having bad fuel run through your engine for a long period can derail its lifespan.

Getting a new engine can range anywhere between $2,000-$4,000, with prices going much higher depending on the type of engine you have. 

Can you recondition old diesel fuel? (How)

Yes, you can recondition old diesel fuel to be used anew. This method is not only safe but is also another way of saving up gas money. 

Old diesel pump and old diesel can't be used anymore

You can do this by mixing the old diesel with a mixture of PRD-D or ether. You must only choose one between the two as using them both is not advisable and will not treat the contaminated diesel.

If you have 50 gallons worth of old diesel, you can use 92.4ml of PRD-D or 8.279 liters of ether for the solution. This is calculated through a ratio of 5.6 oz. of ether, while 0.0625 oz of PRD-D. Both ratio solutions should be applied per gallon of the old diesel fuel.

After mixing them, let them rest for 1-2 days. Here we will be waiting for the PRD-D or ether to clean and render the diesel. After that, you can finally use the old diesel as if it was fresh off the pump. 

Click here to see Hot Shot's PRD-D on Amazon.

How to dispose of bad diesel fuel

Diesel and gasoline are both classified as hazardous materials bot for human and animal consumption. They also pose environmental risk factors; therefore, you cannot just simply dispose of them but throw when in water or on the ground. They are categorized as hazardous waste if unused and therefore should be disposed of with caution.

If you have old and unusable fuel, and you decide to dispose of it, bring it to the nearest fuel refinery for proper disposal and recycling. 

Diesel is one of a hazardous waste

You may also contact hazardous waste collectors or local recycling centers in your area to take the unused diesel off your hands. This way, we can be sure that we will not be releasing dangerous chemicals that can potentially be a health and environmental risk for everyone. 

Can you put WD40 in your diesel tank?

Some use wd40 as a starter solution if they are having difficulty in starting their diesel vehicle, they add WD40 to their tanks to help it go through a cold start. This is because WD40 is highly combustible. When wd40 is added to a gas tank, it travels to the engine and helps in triggering internal combustion for the engine to start.

Click here to see WD-40 on Amazon.

Although there is a plethora of uses for WD40, and it can sometimes be considered a wonder liquid in the mechanical world, it was never designed for such a purpose. 

If you are ever experiencing a cold start, the best option is still to use designated starting fluids for your gas tank. This will ensure that you are using products specifically manufactured for such a purpose.

This assures you that down the road, there will be no negative effects on your car. Another device that you can use alternatively for cold starts glows plugs.

It is a device that uses heating elements that heat fuel and air coming to a diesel engine and promote internal combustion to start. 

Click here to see Glow Plugs on Amazon.

Can you put cooking oil in your diesel tank?

Used oil for cooking

Technically, you can use cooking oil as it is where biodiesel is typically made and synthesized from. You can also use biodiesel as a fuel for all diesel engines, it can serve as a type of substitution or alternative option.

But you must remember that there could be possible side effects as cooking oil is not specifically designed to fuel car engines; they are made for cooking food, that is why they are named so.

It means that you can encounter problems when doing so. This has to do with the viscosity of cooking oil; it is very thick and sticky, especially if it is already used. 

In summary

Diesel engine refueling

Diesel fuel can go bad. Learning how to properly store it will prevent you from putting dirty diesel in your tank. You should also be careful in choosing refueling stations, choose reputable ones, so you can be sure that you are getting clean and pure diesel. 

Here are some articles that we have previously written for you. Go ahead and check them out.

How Long Do Injectors Last On A Diesel?

Do You Need A Diesel Truck To Pull A 5th Wheel [Including 5th Wheel & Pick-up Models]

How To Get Water Out Of A Diesel Fuel Tank


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