What If I Accidentally Put Diesel In My Car?

You’ll require an emergency tow to the mechanic, who will be able to drain the diesel fuel from your tank and clean it with regular gasoline to remove any diesel residue. After the mechanic removes the diesel fuel from the tank, he or she will refuel the engine with standard gasoline and start it.

What happens if you accidentally put diesel fuel in your car?

The first thing you should know is that there are precautions in place to prevent you from using the incorrect type of fuel in your vehicle. Because the nozzles on diesel fuel pumps are larger than those on unleaded gas pumps, a diesel fuel nozzle is unlikely to fit into your gas tank. Furthermore, the handle of a diesel fuel pump is normally marked with a bright green — sometimes yellow — color to ensure that you don’t mix up the pumps.

If you manage to get through these safeguards, a couple of things can happen after you fill your gasoline tank with diesel fuel. Depending on how much gas was left in your tank, you might be able to make it a few miles down the road. However, once the surplus gas in the fuel lines is used up, your engine may shut down, leaving you stranded. This is due to the fact that gasoline engines have a difficult time combusting diesel fuel. Because diesel fuel has a low octane rating, the engine may run rough or knock depending on the level of pollution.

At that moment, calling a roadside assistance provider to be towed to a nearby auto shop is your best bet. The gasoline system can be cleaned and drained there. Emptying the gas tank, cleansing the fuel lines, rail, and injectors, and replacing the fuel filters are all part of this process.

The good news is that emptying and cleaning the system isn’t difficult, and you’re unlikely to cause irreversible damage to the injectors or other components. The bad news is that it might be a more expensive operation, owing to the fact that it is a time-consuming technique.

Let’s imagine, instead of being stuck on the side of the road, you realize your mistake in the middle of filling up your car with diesel. It’s best not to start your car at all in this situation. To discourage the diesel from moving further into your fuel system, avoid revving the engine (or simply turning the key to the “on” position). Rather, have your car hauled straight from the petrol station to the auto shop – but don’t wait!

Will a little bit of diesel hurt a gas engine?

Diesel will not burn in your engine, but it will “cook” if enough gas is present in the mixture to keep the engine running. The carbon in the heavy fuel will “cook” into a sooty, black smoke if the diesel gets very hot but not hot enough to catch fire. On acceleration, many older diesels produced plumes of black smoke due to unburned fuel escaping the engine. If you add a gallon or two of diesel to a tank of gas, your gas engine will do the same thing. It all depends on how much effort you put in. The more diesel in the mix, the more smoke the engine produces… assuming it runs at all.

How do I know if I accidentally put diesel in my car?

So you think you put diesel in your gasoline car; what does this signify for your vehicle? The good news is that putting diesel in a petrol engine should not cause your car any long-term or costly damage, even if you have driven it with a substantial amount of incorrect fuel in the tank. Because the diesel nozzle is often larger than the petrol nozzle, putting diesel in a petrol car is uncommon.

When your gasoline has been contaminated with diesel, your engine may begin to misfire, refuse to start, cut out, or emit a smokey exhaust. If you notice any of the signs indicated above and suspect you’ve put diesel in a gasoline vehicle, STOP DRIVING and turn off your motor as soon as it’s safe to do so. This will prevent the diesel residue from contaminating your engine further.

Petrol is ignited by a spark generated by the spark plugs, unlike diesel, which must be compressed to ignite. The diesel will clog the spark plugs and fuel system if the automobile is started, causing the vehicle to misfire, smoke, and possibly cease running. The bike or car should start pretty fast after the contaminated fuel has been drained from the system. Smoke will appear as the diesel residue is burned off; following that, the car should run as it did prior to the event.

The good news is that putting diesel in a gasoline engine is significantly less dangerous than putting gasoline in a diesel engine. Your engine or fuel system are unlikely to be permanently damaged as a result of your actions. To remove any tainted fuel, a full flush of the fuel lines and tank is required. Your automobile should run fine when this flush has been completed and the residual remnant diesel has been removed from the system. We do recommend changing your gasoline filter within a few days of the occurrence as an added precaution; these are a reasonably low-cost component that is straightforward to install.

Will diesel ruin a gas engine?

The gasoline fuel and air are squeezed together in gas engines and ignited by a spark generated by a spark plug.

There are no spark plugs in a conventional diesel engine. Diesel engines require severe compression, which is created by squeezing the mixture, to generate enough thermal heat to keep the fuel combusting indefinitely. It’s also known as a “compression ignition” because of this.

This is also the primary distinction between how a gas engine and a diesel engine operate.

Fuel efficiency and Price:

In general, a diesel engine is more efficient and powerful than its gasoline counterpart. Although diesel is more expensive than gasoline, costs vary around the United States, and the difference is not as great in other states.

Diesel fuel also has a higher joule-per-unit energy content. As a result, it is more efficient than gasoline because it delivers more energy for the same amount of money.

Power Output:

In terms of power output, the two fuels are likewise vastly different. The engines’ power and torque outputs are measured in horsepower and torque. Whereas an engine’s horsepower is purely a measure of its power, torque is a measure of the rate at which the engine creates force on the driveline through the twisting process.

While both horsepower and torque are necessary for a powerful and efficient engine, a big quantity of horsepower without a corresponding level of torque will cause the vehicle’s acceleration to slow. Torque is the force that moves your car forward and starts the engine. This is why diesel engines are used in huge vehicles like trucks. Vehicles with powerful engines can handle large weights.

Diesel engines, on the other hand, do not rev as high as other fuel engines. They produce less horsepower and are therefore unsuitable for fast cars. Diesel engines produce a lot of torque but not a lot of horsepower, whereas gasoline engines produce more horsepower but not as much torque.

Drive experience:

Gasoline-powered vehicles are generally smoother and provide a better driving experience. As soon as you step on the accelerator pedal, you’ll notice the difference. Diesel vehicles accelerate quickly.


Diesel engines use compression ignition, which is the most significant distinction between them and gasoline engines. Compression ignition is completely unsuitable for a gas engine. In fact, it has the potential to entirely destroy a gas engine. A diesel engine is far more dependable than a gasoline engine since it is built to be harder and more robust. These engines are more resistant to wear and tear. They also require less upkeep and care.

Because it does not need spark plugs, a conventional diesel engine is much simpler and less complicated than a gas engine. A diesel engine is also thought to live longer than a gasoline engine. Furthermore, the number of miles or hours that diesel engines may operate without needing maintenance is far higher.

As a result, it’s reasonable to assume that diesel engines are more efficient, powerful, and dependable than most gas engines. A gas engine, on the other hand, may be preferable for performance and a smoother driving experience.

What happens if I put 1 gallon of diesel in my car?

When you notice you’ve mistakenly placed diesel fuel in your gas tank, you’ll need to act quickly. It’s not a good idea to leave diesel in a gas tank for an extended period of time. Under any circumstances, do not start the vehicle. You should get your vehicle towed to a garage for drainage as soon as possible. Attempting to drive the automobile could result in diesel fuel entering the fuel line and engine system, making the repair process much more difficult and expensive.

This is the perfect circumstance if the vehicle’s petrol tank has a removable drain. The mechanic will simply open the drain and drain all of the gasoline/diesel combination. After that, the tank will be refilled with gasoline before being emptied to remove any residual diesel. To rid the tank of all diesel contaminants, this operation may need to be repeated.

If the gas tank does not have a removable drain, it must be removed from the vehicle and drained. “Dropping the tank” is the term for this. The mechanic will next continuously rinse the tank with fresh gasoline until all of the diesel fuel has been removed.

Depending on whether the tank needs to be dropped and how much fuel is there, draining the tank might cost anywhere from $200 to $500. If diesel fuel has gotten into the fuel line or engine, the cost of repair might easily reach $1,500-$2,000.

How much diesel will mess up a gas engine?

It has an octane rating of 87-91 for automobile engines that use today’s gasoline. When it comes to diesel fuel, it has an octane rating of 25 to 40. When 2% diesel fuel is blended into gasoline, the total ration drops by one point. Most engines would be harmed by diesel contamination of more than 10%, forcing them to fail.

How much diesel does it take to ruin an engine?

Let’s imagine you mix a small amount of gasoline with your diesel fuel by mistake. The first thing it’ll do is lower the flash point of the diesel, which can be harmful because pockets of greater gasoline concentrations can form in a tank. As a result, the flash point would be inconsistent across the tank.

Given the wide difference in flash point temperature between gasoline and diesel, it only takes a small amount of gasoline to drastically lower the flash temperature. Even a 1% gasoline contamination lowers the diesel flash point by 18 degrees Celsius. This indicates that the diesel fuel will ignite early in the diesel engine, perhaps causing harm to the engine.

Contamination with gasoline can harm the fuel pump and cause diesel injectors to malfunction.

This occurs due to a lack of lubrication. To put it another way, gasoline is a solvent, but diesel is an oil. Diesel has enough lubricity to keep the fuel pumps and injectors lubricated. By replacing the oil with gasoline, the lubrication is lost, resulting in damage.

Beyond them, you’ll get incomplete combustion, which produces a lot of black smoke at first. Beyond being a cosmetic issue, the vehicle’s computer will modify the fuel-air combination to compensate for the absence of combustion. This will significantly reduce your power and performance. Furthermore, if you continue to use the fuel, you risk overheating or covering the vehicle’s computer sensors in soot that they become unable to detect anything.

Putting Diesel into Gasoline

Now consider the opposite situation: you’re mixing a higher flash, heavier fuel with a lighter, more volatile base fuel (gasoline) that burns at a much lower flash temperature. Some may believe that this “diesel-in-gasoline” scenario is less dangerous than the opposite. However, this is not the case.

The loss of octane is a major concern when gasoline is contaminated with diesel fuel. When considering how gasoline burns in an engine, the octane rating is a gauge of the fuel’s ability to ignite at the proper moment – not too soon. Once pumped into the chamber, gasoline with a lower octane rating will ignite too rapidly. The gasoline ignites and explodes, but the piston is still rising, and the subsequent pressure wave collision causes a knocking sound (at best) and damage to the piston and rod (at worst). Octane, in a way, slows down and delays combustion.

To match today’s car engines, gasoline must have an octane rating of 87-91. The octane rating of diesel fuel is 25-40. By mixing 2% diesel fuel with gasoline, the overall octane rating is reduced by one point. The octane of diesel that has been contaminated by 10% drops by 5 points, which is enough to cause issues in most engines. With increasing percentages of diesel fuel in gasoline, the octane depression rises linearly.

  • Because diesel fuel is heavier than gasoline, it might settle to the bottom of your gas tank, causing both gas and diesel to be injected into the intake manifold or cylinder. Partially-burned diesel fuel, depending on the mix, can leave large deposits on pistons, valves, and spark plugs. You buy a car or truck that runs poorly, and if you continue to drive it, you risk catastrophic harm.
  • If enough diesel fuel gets into the cylinders, the cylinders can hydro-lock, resulting in a blown head gasket, broken cylinder head, or other catastrophic issues that can lead to your vehicle’s premature death.
  • This diesel fuel can seep through the piston rings and into the oil crankcase, diluting the lubricating oil. This can cause damage to all lubricated internal engine elements, resulting in significant engine failure due to accelerated wear.
  • Unburned diesel fuel will ignite in the catalytic converter if it enters the exhaust system unburned. The fire will fill the holes in the catalyst, ruining it and costing you thousands of dollars to replace.

The Bottom Line – Don’t Drive It

Because it’s hard to tell how much of the improper kind of fuel is in your tank and fuel system, the best advice is to have your car towed to a mechanic’s garage where the problem may be fixed.

They will remove all of the fuel from the filter and flush the system to remove the issue fuel once they arrive at the garage.

Some could say, “Well, my (fill in the blank with a friend, coworker, relative, or general practitioner) got some in his tank by accident, and he drove it and it was OK.”

There’s no way to determine how your circumstance compares to theirs in certain instances (and human nature dictates that we downplay our descriptions of prospective difficulties if they arise from a mistake we’re responsible for).

You have been told not to drive the car if you believe the improper gasoline has been dispensed. In any event, we advise you to avoid taking that risk.

Are diesel nozzles bigger than gas?

Because diesel nozzles are larger than gasoline nozzles, they will not fit in your gasoline vehicle’s tank. The tiny gasoline nozzle will readily fit into diesel filler necks, thus diesel drivers should exercise particular caution.