What Happens if you put Diesel in a Gasoline Car?

Accidentally putting diesel fuel in a gasoline-powered vehicle is a more common mistake than one might think, especially since many fuel pumps often house the gas nozzle right next to the diesel nozzle. If a driver is not paying attention, they can potentially grab one over the other and attempt to pump the wrong kind of fuel into their tank.

However, this is not necessarily an easy mistake to make because diesel pumps are generally labeled in a vibrant green to differentiate themselves. Also, a vehicle's gasoline filler neck and the diesel fuel nozzle are purposely designed to be incompatible. Meaning, the diesel dispenser is too large to fit into a gasoline filler neck easily. Regardless, some people still somehow manage to pour diesel fuel into their gasoline tanks.

When diesel contamination occurs, it can have severe consequences on a conventional gasoline-powered vehicle's health and operation.

Gasoline vs. Diesel

In terms of application, diesel is most often used by heavy-duty trucks, semis, buses, boats, and vehicles which may require a higher torque rating and more low-end pulling power. Gasoline powertrains are most often associated with passenger cars, SUVs, and light-duty trucks.

Although they are both derived from crude oil, gasoline and diesel have different physical properties. Gasoline is much thinner and has a distinct odor. Diesel fuel has a thicker state of fluidity, almost like a lightweight oil. These physical differences come into play when diesel attempts to make its way through a gasoline vehicle's fuel system and engine components.

Diesel is also not as combustible as gasoline. Since each fuel has its own autoignition temperature, diesel and gasoline engines work differently. A gasoline engine utilizes spark plugs to ignite the fuel, while a diesel engine uses the pressure created by compression within the engine to ignite fuel (though a part called a glow plug might help when the engine is cold). In other words, diesel is heated up by being squeezed, while gasoline is lit with fire. Furthermore, gasoline is often mixed with as much as 10-percent ethanol, a highly flammable organic compound used as a biofuel additive. Ethanol makes gasoline even more combustible than it already is.

In short, gasoline and diesel engines are designed to operate using only their specific fuel-type and not the other.

What Happens if You Put Diesel in a Gas Car

Since diesel fuel is thicker and denser than gasoline, the fuel pump will struggle to move the diesel/gasoline mixture through the system. Also, the diesel will not be able to easily pass through the fuel filter. Instead, it will clog up the fuel filter. And whatever amount of diesel that then makes its way to the engine will clog the fuel injectors, making them inoperable. This will result in the engine gumming up and seizing. The gasoline engine may run for a little while after diesel has been put in the tank, but that is only because it is still running on the fuel line's remaining gasoline.

As bad as that situation may be, the opposite problem – pouring gasoline into a diesel tank – would be far worse. Because of gasoline's high combustion tendencies, it would ignite much sooner than diesel fuel would. This early ignition and volatility could cause catastrophic damage to the diesel engine and its components.

What to Do if You Put Diesel in a Gas Engine

If you accidentally put diesel fuel into your gas tank, immediate action is necessary: 

• First and foremost, DO NOT START the vehicle under any circumstance. 
• Have your vehicle towed to a garage for fuel drainage right away. 

Attempting to operate the car could cause the diesel fuel to enter the fuel line and the engine system, which will make the repair process far more complicated and costly.

Please note that leaving diesel in a gas tank for any length of time is not advisable. There are two drainage options depending on your vehicle: either your vehicle’s gas tank has a removable drain, or the gas tank needs to be removed to drain the diesel.

Removable Drain Gas Tank: Ideally, your vehicle has a removable drain on the gas tank, which makes the drainage process much smoother. The mechanic simply opens the drain and empties the entire amount of the gasoline/diesel mixture. The tank is then filled with gasoline and drained again to remove all remaining diesel. This process is repeated until the tank is cleared of all diesel contamination.

Gas Tank Removal: If there is no removable drain on the gas tank, the tank has to be removed from the vehicle and drained. This is called "dropping the tank." The mechanic then rinses the tank repeatedly with fresh gasoline until all the diesel fuel is washed out.

How Much Does It Cost to Fix?

The cost of resolving the issue depends on how quickly you respond to the situation. For instance, if you address it immediately and don’t turn on your vehicle, your costs will be for towing and draining the fuel tank. Draining the tank could cost anywhere from $200 to $500 depending on whether the tank needs to be dropped and how much diesel is present. Towing the vehicle could add about $100 to the total. However, the towing portion may be covered if you have a roadside assistance program such as AAA. There is a chance that your membership in a roadside assistance program also covers fuel draining, but most insurance plans don’t cover expenses related to misfuelling. 

If diesel fuel has entered the fuel line or engine, then other components are impacted. In this situation, the repair job can easily climb into the thousands. Vulnerable parts include the catalytic converter, fuel pump, and fuel injector. Catalytic converter replacement alone could cost $800 to $1,200. Meanwhile, fuel pumps have a bigger range in replacement prices from $220 to $1,110, including labor. A fuel injector replacement might set you back $300 to $900. Thus, if these three parts need to be replaced, it could cost roughly $1,320 on the lower end to $3,210 on the higher end. This is all the more reason to take immediate action by not turning on your vehicle and having it towed to a repair shop.

Summary

If you accidentally put diesel into a gasoline car, or you learn the gasoline was contaminated with diesel, do not panic. You aren’t the first person to be in this situation. Remember to not turn on the vehicle and have it towed to a local shop to have the oil tank drained. The sooner you identify and respond to the issue, the sooner you can isolate the situation and prevent the diesel from leaving the gas tank and impacting other vehicle components. 

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