What Happens When You Put Diesel In Your Car?

You don’t want the diesel fuel to be drawn into your engine by the fuel pump since it can clog your fuel system and maybe damage the moving parts in your engine block. Your car will be alright as long as you take steps not to start it after adding diesel fuel to your tank.

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.

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.

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.

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.

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.

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.

What will happen if I put the wrong fuel in my car?

The most important thing to remember if you put gasoline in a diesel automobile is to not start it. The fuel will flow through the engine once it is started, causing havoc on the entire system. Before you drive the car, you must drain the fuel tank.

The gasoline will act as a solvent, causing the fuel pump and other components of the fuel system to be damaged. If left unchecked, a costly fuel system repair or a complete replacement of the fuel pump, diesel injectors, filters, and fuel tank may be required.

Does diesel go bad?

There are two issues here. First, because diesel fuel is a carbon-based petrochemical, it begins to oxidize as soon as it leaves the refinery, forming the sediments and gums that choke fuel. So, how long will a gallon of diesel fuel last? Without diesel fuel additives, diesel can go bad in as little as 30 days, causing deposits that can harm fuel injectors, fuel lines, and other system components, reducing fuel economy and performance.

Water is a significant issue in diesel fuel for several reasons. One is that new diesel mixes frequently include biodiesel, which has a higher water content by nature. If the water isn’t separated from the fuel, it can make its way into the fuel injectors. Pressures of up to (40,000) PSI are used in newer common rail fuel systems. If even a single droplet of water makes its way to the fuel injector through one of the new high-pressure systems, it can blow the tip-off, which is an expensive repair. This slime, like oxidation, can clog the fuel and cause long-term damage.

You can reduce the amount of water in your tank by keeping it full, which reduces the amount of condensation area in the tank and thus the amount of water. Second, diesel fuel treatments that demulsify or separate water from the fuel are available. A Fuel Water Separator (FWS) filter is found in almost all diesel engines. The performance of the body is improved by demulsification (FWS). All OEM manufacturers recommend demulsifying diesel fuel to ensure that water may be properly removed without causing damage to your engine. For fuel storage tanks, standard good fuel maintenance standards must be followed. These procedures entail the removal of water that has accumulated at the tank’s bottom on a regular basis. Because water is heavier than fuel, it will sink to the bottom, where it will be safer than in your fuel system. To avoid microbial growth, maintenance dosages of a dual phased (works in both water and fuel phases) biocide should be applied twice a year.

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.