What If I Accidentally Put Diesel Fuel 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.

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 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!

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.

Will a small amount of diesel damage a petrol engine?

The industry typically views 5% or less of diesel in gasoline as a safe amount. If the engine starts, it will be strained because the diesel in a hot engine will combust too quickly, causing the engine to operate hotter than it was designed, perhaps damaging the pistons and other components.

Will my car start if I put the wrong fuel in?

Most diesel fuel pumps will not fit into a petrol filler neck, thus this is an unusual occurrence. However, do not start the engine if you put diesel in a petrol car’s fuel tank because this will allow the fuel to circulate and contaminate the fuel system.

The dangers of putting diesel in a gasoline car are less severe than the reverse. Diesel is a heavier, oilier fuel than gasoline, and it is more difficult to ignite in a gasoline engine. The engine may not start if the diesel is allowed to circulate throughout the fuel system.

The majority of repairs will begin with a complete fuel tank flush to remove any contaminated fuel.

Can diesel and petrol mix?

When it comes to the improper gasoline in the car cost equation, this is both the most prevalent and, unfortunately, the most fatal mistake.

Because the petrol nozzle will really fit into the filler for a modern diesel, misfueling a diesel automobile with petrol is easier to perform (especially if you approach the fuel pumps with your eyes closed).

If you use unleaded gasoline in a diesel engine, you risk causing major and maybe fatal harm to your vehicle. That’s right, it’s that horrible.

When you mix petrol with diesel in your tank, you’re essentially generating a solvent, which will immediately cause havoc with your car’s fuel system, perhaps necessitating the purchase of a new engine, filters, fuel pump, injectors, and a whole new fuel tank.

Modern common-rail diesels are particularly vulnerable to this type of damage, which is cruel because these more sophisticated engines don’t sound as rattly as older engines and may lead you to forget you possess a diesel vehicle.

Putting a gun to the head of your car and pressing the trigger is a good analogy for putting gasoline in a diesel engine.