Cautions of Putting Engine Oil in Diesel Fuel Tank

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Putting engine oil in a diesel fuel tank may appear a strange technique, but a good deal of diesel car owners do it. Typically, diesel owners will add 2-stroke or engine oil in their diesel fuel tank to lubricate the fuel itself. It also covers the top part of the engine cylinders.

However, it’s not always recommended to put engine or 2-stroke oil in the diesel tank. Before mixing diesel fuel and engine oil, you must thoroughly know their pros and cons. Also, you should know the right technique to use engine oil in the diesel fuel tank.

Thus, we will explore all the questions in today’s article. If you are considering adding fully-synthetic engine oil to a diesel fuel tank, continue reading for a complete understanding.

What Is Engine Oil?

Engine oil is essentially a type of lubricant. It is required for the proper functioning of an engine. The engine oil or lubricant works as a protective layer between metal surfaces. So, it reduces friction and wear during operation. It also reduces heat to keep the engine parts cool.

You will mainly find three types of engine oils. These are:

  • Mineral engine oil comes directly from crude oil with minimum refining.
  • Semisynthetic oil has a balance between industrial chemical processing and crude oil mixture.
  • Fully-synthetic oil is made through complete chemical processes without any crude oil.

What Is Diesel Fuel?

Diesel fuel is mainly a petroleum-based fuel. It is commonly used in diesel engines because it has a higher energy density than gasoline. As a result, diesel fuel is more efficient at producing power. Manufacturers produce diesel fuel from crude oil through the distillation process.

Several types of diesel fuels are in the market, all based on sulfur’s presence. The list includes:

  • Low sulfur diesel (LSD): LSD contains up to 500 parts per million (ppm) sulfur. So, it is not so eco-friendly.
  • Ultra-low sulfur diesel (ULSD): ULSD contains less than 15 ppm of sulfur. Thus, it reduces harmful emissions and is eco-friendly.

Diesel fuel, with its higher energy level and efficiency, is important in powering many transportation industries worldwide.

How Can Putting Engine Oil In Diesel Fuel Tanks Be Helpful?

Although engine oil is used as an engine lubricant, it is beneficial to add to diesel fuel tanks. The reason for this lies in its chemical properties. Engine oil contains detergents, dispersants, and anti-wear agents. All these chemicals will clean and protect the engine components.

When you add engine oil to a diesel fuel tank, it helps improve the overall performance of the engine. First, the engine oil will reduce friction between moving parts. It results in smoother operation and improved fuel efficiency. As the engine oil gets mixed with the diesel, they cover the engine cylinders, which are prone to faster wear and tear.

With its additives and protective nature, engine oil flows with diesel over metal cylinders. So, cylinders have less friction, and in turn, it increases their lifespan.

Moreover, adding engine oil to diesel fuel can reduce engine emissions. The detergents present in the oil will keep the injectors clean. Thus, it promotes more efficient combustion. It leads to less harmful emissions being released into the atmosphere. As a result, your vehicle becomes more eco-friendly even with diesel fuel.

No doubt, using engine oil in a diesel fuel tank may seem like an unconventional approach. Yet, it offers numerous benefits without any significant drawbacks. However, you shouldn’t use engine oil with diesel fuel without the consultation of a mechanic or anyone already used the mixture.

It is vital since you need to mix the diesel fuel and engine oil in an appropriate proportion. Or else, your engine may stop working and stall, which will be a costly repair and maintenance task.

putting engine oil in diesel fuel tank

What Are The Benefits Of Using Engine Oil In A Diesel Fuel Tank?

Using engine oil in a diesel fuel tank has several benefits. From increasing lubrication to improving the fuel efficiency of your engine, this mixture is a magic spill for your vehicle.

Increases lubrication:

Mixing engine oil with diesel fuel increases the lubrication of the engine’s moving parts. Diesel engines generally exhibit higher compression ratios compared to gasoline engines. This disparity in compression ratios is a characteristic feature of diesel engines and distinguishes them from their gasoline counterparts. Therefore, they require more lubrication to function properly. Adding engine oil will reduce friction and prevent excessive wear and tear on the engine.

Engine oil is derived from crude oil through a refining process. Crude oil possesses corrosive characteristics, which are mitigated during the refining process to produce engine oil. . As you add engine oil, this corrosive feature of diesel fuel reduces. You should choose high-quality engine oil for the best results. Regarding this, you must know, Is Kirkland synthetic oil as good as Mobil 1?

Improves fuel efficiency:

When you put engine oil in a diesel fuel tank, it will improve fuel efficiency. It happens as the engine oil acts as a detergent. So, the detergent and surfactant keep the injectors clean with reduced deposits and buildup.

Clean injectors allow better atomization of fuel during combustion. It results in improved performance and increased mileage. So, your cost of fuel will reduce quite considerably.

Increases octane-rating of the fuel:

You may consider adding small amounts of high-quality synthetic or semi-synthetic oils to your diesel fuel tank. Although it’s unconventional, it will indeed improve the octane rating. So, the diesel fuel will ignite faster under pressure – leading to smoother operation and reduced emissions.

As you see, putting engine oil in a diesel fuel tank will significantly improve the performance and longevity of your vehicle. Plus, it helps you save some cash at the pump!

Are there any drawbacks to putting engine oil in a diesel fuel tank?

No doubt, using engine oil in a diesel fuel tank has benefits. However, you should also consider some potential drawbacks.

  • Firstly, engine oil in a diesel fuel tank might damage the engine if used excessively. Only a small amount of oil help with lubrication and cleaning. However, its overuse can clog filters and damage injectors.
  • If you use non-approved additives like engine oil, it can void any warranties on your vehicle. So, you should check your owner’s manual before adding anything other than diesel fuel to your tank.
  • Another possible disadvantage is the effect on emissions. This aspect can have negative consequences, particularly in terms of the environmental impact caused by emissions. Engine oils contain chemicals that are not meant for combustion. Thus, at times, it may increase harmful emissions.

How To Use Engine Oil In A Diesel Fuel Tank

You must be cautious when you decide to put engine oil in the diesel fuel tank. If you overuse it, the additive might cause damage to the engine parts. You can avoid such things with the following recommendations.

  • You must have the correct type of engine oil for the diesel tank. So, check your manufacturer or mechanic to determine the right type and viscosity of the oil.
  • You should only pour a small amount of the engine oil into the fuel tank. The recommended ratio is about 1 quart per 100 gallons of diesel fuel.
  • Mix the contents thoroughly by driving around or shaking the vehicle gently. It ensures that the oil mixes well with the fuel.
  • Monitor your vehicle’s performance after adding engine oils. If you notice any changes in vehicle performance, contact a qualified technician immediately.


Is putting engine oil in a diesel fuel tank recommendable and safe? Yes, adding engine oil with diesel fuel is recommendable only under the supervision of an expert automobile technician. You may start with 1 quart of engine oil with 100 gallons of fuel and see the effect.

You will appreciate the improved fuel economy, reduced emissions, along with wear and tear. So, your engine will deliver better performance and last longer.

Frequently Asked Questions(FAQs):

Q: What happens if I put engine oil in a diesel fuel tank?

A: Engine oil is not designed to be used as a fuel. If you accidentally pour engine oil into your diesel fuel tank, it can lead to engine damage and potentially cause a breakdown. The oil does not combust properly and can clog fuel injectors, filters, and other fuel system components.

Q: What are the potential consequences of running the engine with oil-contaminated diesel fuel?

A: Running the engine with oil-contaminated diesel fuel can lead to severe engine damage. It can cause increased friction, poor lubrication, and potential overheating, which may result in costly repairs or even engine failure.

Q: How can I prevent this mistake from happening?

A: To avoid accidentally putting engine oil in the diesel fuel tank, it’s important to practice good fueling habits. Keep engine oil and fuel containers clearly marked and stored separately. Additionally, always double-check before adding any fluids to your vehicle to ensure you’re using the correct product for the intended purpose.

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