What Happens If You Put E85 In A Diesel Engine

If you own a diesel engine, you know that it requires a specific type of fuel. Putting the wrong fuel in your engine can lead to serious problems and costly repairs. But what if you accidentally fill your tank with E85 fuel instead of diesel? What happens then?

In this article, we’ll explore the consequences of putting E85 in a diesel engine and what you can do to prevent and fix this mistake.

Before we dive into the consequences, it’s important to understand what E85 fuel is. E85 is a blend of ethanol and gasoline, with the ’85’ referring to the percentage of ethanol in the mixture. This fuel is primarily used in flex-fuel vehicles, which are designed to run on either gasoline or E85.

However, it should never be used in a diesel engine. Diesel engines are designed to run on diesel fuel, which has a much different chemical makeup than E85. Mixing the two fuels can have serious consequences for your engine’s performance and longevity.

Understanding E85 Fuel

You’ll be surprised to know that E85 fuel, a blend of ethanol and gasoline, can be a great option for non-diesel engines. Ethanol is a renewable fuel that’s made from plants such as corn, sugarcane, or sorghum. E85 fuel contains 51-83% ethanol, which makes it a cleaner-burning fuel than gasoline alone.

However, it’s important to note that using E85 fuel has both pros and cons. One of the biggest pros of using E85 fuel is its environmental impact. Ethanol is a renewable resource, which means that it can be produced in a sustainable way. Using E85 fuel in non-diesel engines can reduce greenhouse gas emissions, as it burns cleaner than gasoline.

However, the downside of using E85 fuel is that it can decrease fuel economy, as it has less energy content than gasoline. Additionally, not all vehicles are designed to use E85 fuel, so it’s important to check with your manufacturer before using it.

Diesel Engines vs. Ethanol

If you’re considering using ethanol in your diesel engine, there are a few key differences to be aware of. First, ethanol has a lower energy density than diesel, which means you’ll need to use more of it to achieve the same level of power.

Additionally, diesel engines are designed differently than those that run on ethanol, so there may be compatibility issues to consider.

Finally, it’s important to note that not all diesel engines are capable of running on ethanol, so be sure to check with your manufacturer before making any modifications.

Differences in Energy Density

Now, using e85 in your diesel engine will result in a noticeable difference in energy density. Ethanol has a lower energy density than diesel, which means that it contains less potential energy per unit of volume.

The energy density of diesel is around 35.8 megajoules per liter, while the energy density of e85 is around 25-27 megajoules per liter. This means that if you use e85 in your diesel engine, you will need to use more fuel to achieve the same power output as with diesel.

Moreover, the difference in energy density between diesel and e85 affects the combustion efficiency of the engine. Combustion efficiency refers to the ability of the engine to convert the fuel into power without wasting too much energy in the form of heat or emissions.

When you use e85 in a diesel engine, the lower energy density of e85 means that the engine will have to work harder to achieve the same power output as with diesel. This can lead to lower combustion efficiency, higher fuel consumption, and increased emissions.

Ultimately, using e85 in a diesel engine is not recommended due to its lower energy density and negative impact on combustion efficiency.

Engine Design and Compatibility

Accidentally putting E85 fuel in a car designed for gasoline can be a common mistake. However, it is important to note that E85 is not compatible with diesel engines. Flex fuel vehicles, on the other hand, are designed to run on a blend of gasoline and ethanol, which includes E85 fuel. This means that flex fuel vehicles can utilize E85, but diesel is not suitable for them. If you were to put diesel in a flex fuel vehicle, it could lead to severe damage to the engine. Diesel fuel has different properties compared to gasoline or ethanol, and the engine components in a flex fuel vehicle are not designed to handle diesel fuel. Similarly, you cannot run E85 in a diesel engine. The combustion characteristics and fuel properties of E85 and diesel are significantly different. Introducing E85 into a diesel engine would likely cause misfires, loss of power, and potentially damage the engine. It is crucial to always use the proper fuel for your vehicle. Putting ethanol or E85 in a diesel engine can have disastrous consequences. Diesel engines require diesel fuel, which is specifically formulated to suit their combustion process. To summarize, E85 is a type of fuel blend that contains ethanol and is suitable for use in flex fuel vehicles designed to run on this specific blend. However, E85 is not compatible with diesel engines, and using E85 or ethanol in a diesel engine can result in engine damage or failure. Therefore, it is essential to use the correct fuel for your vehicle to ensure optimal performance and avoid expensive repairs.

To ensure proper function and avoid damage, it’s important to check your vehicle’s owner’s manual and consult with a qualified mechanic before attempting to use e85 fuel in your diesel-powered vehicle. This is because fuel compatibility is a crucial factor to consider when it comes to engine performance.

E85 is a fuel blend that contains up to 85% ethanol and 15% gasoline, which is significantly different from diesel fuel. The engine’s internal components, such as the fuel injectors and fuel pump, are designed to operate with diesel fuel, not e85. Using e85 in a diesel engine can cause damage to these sensitive components and lead to engine failure.

Moreover, engine modification may be necessary to use e85 fuel in a diesel engine. Ethanol has a lower energy density than diesel fuel, which means that a higher volume of e85 is required to produce the same amount of power as diesel fuel. This can result in poor fuel efficiency and reduced engine performance.

To address this issue, modifications such as engine tuning and fuel system upgrades may be required to optimize the engine’s performance with e85 fuel. In conclusion, it’s important to ensure fuel compatibility and consider engine modifications before attempting to use e85 fuel in a diesel engine to prevent damage and optimize performance.

Consequences of Putting E85 in a Diesel Engine

Putting E85 in a diesel engine can cause serious damage and should be avoided at all costs. E85 is a fuel blend that contains up to 85% ethanol, while diesel fuel is a petroleum-based product. The two fuels have different chemical properties and are not compatible with each other.

If E85 is put into a diesel engine, it can cause fuel contamination, which can lead to engine failure. Fuel contamination occurs when the wrong fuel is added to a vehicle’s fuel tank. When E85 is added to a diesel engine, it can cause the fuel system to clog and corrode, leading to costly repairs.

The engine performance can also be affected, leading to reduced power and efficiency. To avoid these consequences, it’s essential to use the correct fuel for your vehicle. If you accidentally put E85 in a diesel engine, it’s recommended to drain the fuel tank and flush the fuel system to prevent further damage.

What to Do if You Accidentally Put E85 in Your Diesel Engine

If you’ve accidentally put E85 into your diesel engine, don’t start the engine. This is crucial because the E85 can cause severe damage to the fuel system and engine components.

The next step is to drain the fuel tank completely.

Finally, clean the fuel system thoroughly to avoid any residual E85 from causing further damage.

Do Not Start the Engine

Starting the engine after putting E85 in a diesel engine can cause serious damage. It’s important to take safety precautions and not start the engine at all.

The high alcohol content of E85 can damage the fuel system components of the diesel engine such as the fuel lines, pumps, and injectors. The engine may not start or may run poorly, causing significant damage.

To avoid potential damage, it’s recommended to drain the fuel tank and replace the fuel filter. This will ensure that all traces of E85 are removed from the fuel system.

If the engine has been started, it’s important to immediately turn it off and have it towed to a mechanic for inspection and repairs. Ignoring the warning signs and attempting to drive the vehicle can result in catastrophic engine failure, leading to expensive repairs and possibly even safety hazards on the road.

Drain the Fuel Tank

To avoid causing serious damage to your vehicle, it’s crucial to drain the fuel tank after accidentally filling it with E85. Failure to do so can lead to fuel system contamination, resulting in costly repairs.

The fuel system of a diesel engine isn’t designed to handle high ethanol content, and using E85 can cause damage to the engine and other components. Draining the fuel tank is the first step in fixing the problem. It’ll remove the contaminated fuel and prevent it from entering the engine.

However, simply draining the fuel tank may not be enough. The fuel lines, fuel injectors, and other components may also be contaminated with E85. To ensure that your vehicle is free of any contamination, it’s recommended that you take it to a professional for fuel system cleaning. This will ensure that all components are thoroughly cleaned, and any damage is identified and repaired.

Clean the Fuel System

Cleaning the fuel system is essential to ensure that all components are free of contamination and in good working condition. Fuel contamination is a common issue that can cause significant damage to the engine and its components. When E85 is mistakenly added to a diesel engine, it can lead to extensive damage to the fuel system.

Therefore, it’s crucial to clean the fuel system thoroughly to prevent any further damage. Fuel system maintenance involves removing any contaminated fuel and cleaning the fuel filters, injectors, and pumps. The process may also require using specialized cleaning agents to thoroughly clean the fuel system.

Regular fuel system maintenance is essential to prevent any contaminants from entering the fuel system and causing damage. Taking these preventive measures can help extend the life of the fuel system and keep the engine running smoothly.

Preventing Future Fuel Mix-Ups

Make sure you double-check the fuel type before filling up to avoid any future fuel mix-ups that could cause damage to your engine. Fuel labeling is crucial in preventing any confusion. Make sure to read the label carefully before refueling your diesel engine.

E85 is not compatible with diesel engines and could cause serious damage to your engine. Proper fuel storage is also important in preventing future fuel mix-ups. Keep your diesel fuel in a separate, labeled container away from other fuel types.

This will help ensure that you do not accidentally use the wrong fuel type when refueling. By taking these precautions, you can prevent costly engine damage and maintain control of your vehicle’s performance.


In conclusion, putting E85 in a diesel engine can have serious consequences. It’s important to understand the differences between diesel and ethanol fuels before refueling your vehicle. Ethanol fuels have a lower energy content and a higher octane rating than diesel, which can cause engine damage, reduced performance, and poor fuel economy.

If you accidentally put E85 in your diesel engine, it’s crucial to stop driving immediately and have your vehicle towed to a mechanic. The fuel system will need to be flushed and cleaned to prevent long-term damage.

To prevent future fuel mix-ups, always check the label before fueling and avoid using a fuel container that’s been previously used for a different type of fuel. By following these precautions, you can ensure the longevity and performance of your diesel engine.