What Happens if you put Gas in a Diesel Engine?

Have you ever wondered what happens if you put gas in a diesel engine? Or maybe you have been a victim of this act before, and you experience the effects the hard way (don’t blame yourself or your driver; it happens often). Either way, mixing gasoline and diesel in a vehicle can give headaches and cause catastrophic engine damage.

Accidentally mixing gasoline and diesel fuel is a common mistake one may think of, especially in a gas station where gasoline and diesel pumps are placed next to each other.

In this article, we’ll discuss at length the possible effects of mixing both fuel types in a vehicle and how to test for gas in diesel fuel.

What happens if you mix Gasoline and Diesel?

If you have a vehicle and have been dealing with fuel long enough, you might have mixed these two fuel types.  Mixing gasoline and diesel fuel is not advisable, and it isn’t necessarily a big problem as always projected.

But the question is, how much did you put in? Will a little gas hurt a diesel engine? Let’s find out.

gas in a diesel engine fix

Effects of gasoline in diesel engine

If you notice this problem on time, you may be able to save your engine from severe damage. On the flip side, if you keep driving for a long period with mixed or wrong fuel in your diesel gas tank, then you may experience the outlined effects below.

  • No ignition: Diesel engines are not designed to ignite gasoline fuels, and gasoline engines are not designed to ignite fuels automatically. (It requires a spark to ignite the fuel). Therefore when you pour gasoline into a diesel engine, there will be no spark to ignite it. If, by chance, ignition takes place, since both fuels are mixed up, it will be too little for smooth engine operation.
  • Black smoke: The minimum temperature needed for gasoline to ignite is -40 degrees centigrade, while diesel is 52 degrees centigrade, so it’ll be difficult for gasoline to combust in a diesel engine. This will lead to a huge amount of unburned fuel.
  • As a result of a large amount of unburned fuel, there will be a lot of black smoke from the exhaust tailpipe. This smoke will look embarrassing and smells bad. If you ignore it for long, it’ll clog various fuel system sensors because of soot.
  • Shock wave damage: There are several engine-moving components and parts in both diesel and gasoline engines, such as pistons, con rods, camshafts, crankshafts, pushrods, and wrist pins. If an unusual detonation occurs, the shock wave from the occurrence could damage these engine parts. This can also cause engine knocking.
  • Fuel system damage: If gasoline finds its way to your diesel gas tank, it will cause damage to your fuel pump, injectors, and fuel filters. These are the main components of a diesel fuel system. If they are not working as they should, you’ll need to replace your entire fuel system components for peak performance.
  • Inadequate lubrication: It is unclear to many people that diesel is a kind of ‘Oil’ that lubricates engine components and gasoline is a solvent. Therefore, if you put gasoline in a diesel engine, it’ll lead to a lack of lubrication.
  • If you have wondered what happens if you put gas in a diesel engine or truck, the answer is metal-to-metal contact due to inadequate lubrication. As the metals rub against each other, it will cause damage to reciprocating engine components.
  • Engine damages: If you notice you mistakenly put gasoline in a diesel engine on time, you can salvage your engine before the damages go beyond repair.  But if you continue driving with it for long, you may end up damaging entire engine components. And as you know, a car engine is one of the most expensive components in a vehicle.

gas in diesel engine repair cost

Effects of diesel in a gasoline engine

As gasoline in a diesel engine will cause catastrophic engine damage if left for a long period, diesel in a gasoline engine will cause damage as well. However, the damages are not much because it’s not as bad compared to the effects of gasoline in a diesel engine. (That doesn’t mean you should mix the fuel).

Most diesel gas station nozzles are usually bigger than gasoline nozzles; they’ll hardly fit in. That makes it less common to put diesel in a gasoline engine accidentally.

Fuel system and plug damages: Since gasoline fuel systems are meant to transport petrol, putting the wrong type of fuel in it will eventually cause premature failure to the fuel pump, fuel filter, and injectors. Over time, these components will go bad and require you to replace the entire fuel system components.

Poor/lack of ignition: A diesel in a gasoline engine will cause poor ignition. This is true; even in real life, gasoline ignites faster than diesel fuel.

Car won’t start:  A large amount of diesel in a gasoline engine will eventually prevent your vehicle from starting. If your car won’t start due to diesel in your gasoline fuel system, the best way of fixing it is by draining out the mixed fuel and refilling it with gasoline fuel.

What do you do if you put gas in a diesel engine?

If you have mistakenly poured gas into a diesel engine, or diesel in a gasoline engine, you may be searching for gas in a diesel engine quick fix. Here’s what to do if you mix both fuel types.

Do not start the car: starting the vehicle can cause severe engine damage. Instead of starting the car, remove the keys from the ignition.

Take the car to a safe zone: If you’re still at the filling station when you notice it, put the car in neutral and get someone to assist you, and push it to a safe zone.

Call your mechanic: Once you have pushed the car to a safe zone, contact your mechanic to toll it to a garage. They should drain the wrong fuel and pour the right one. Ensure they put enough of the right fuel to keep you going.

small amount of gas in diesel engine


What’s a worse case in diesel in a gasoline tank?

If you accidentally put diesel in a gasoline tank, the engine will run smoothly until all the gas in the line gets used up. At this point, the engine will run sluggishly or shut down. Gasoline engines are designed to combust petrol, so the engine may start but won’t stay running, or it may not start at all.

Will a small amount of gas hurt a diesel engine?

It all depends on the quantity. So, can you dilute diesel with gas? 1% of gas in a diesel engine may not cause any damage. However, a bigger amount of gas in diesel can cause catastrophic engine damage. This is because a bigger volume of at least 5% will prematurely ignite during the combustion cycle.

Why are gas engines better than diesel?

Generally speaking, diesel-powered engines are more powerful than gasoline ones. This is because diesel engines carry more energy than petrol engines; a quart of diesel fuel has 30% energy more than gasoline.  Diesel engines provide more torque than petrol-powered ones.

Diesel engines also outperform gasoline-powered engines and offer better fuel economy. Then, why are gasoline engines better than diesel engines? Diesel engines suffer performance issues when you pour in black diesel, bio-diesel, or any type of enhanced diesel fuel. This can damage your injector pump and nozzles – and these components are very expensive.

Another reason why people consider petrol-powered engines are, that you can hardly differentiate well-refined diesel fuel from black and bio-diesel.

How can you tell gas from diesel?

Diesel and gasoline fuels have different colors. If you can’t differentiate the colors, just smell them. They have a different smell, if you can’t tell the difference from the smell, deep your fingers in them. Diesel is oilier, while gasoline will evaporate quickly and leave your fingers cold and white.

Can you put diesel in a container that used to have gas?

A small amount of diesel won’t prevent your gasoline from burning as it should. It won’t make any difference to the engine’s smooth operation. However, before using the container, make sure you pour out all the gasoline in it.

How much does it cost to flush diesel out of a car?

Depending on your car make and model and the quantity of diesel in your gas fuel system, you can spend around $400 to $1000 on a fuel system flush, which is what you need to salvage your engine from catastrophic damages.

Final Thoughts

Now that we’ve uncovered what happens if you put gas in a diesel engine, it is of utmost importance to take precautions. Accidentally if you mix these fuels, do not start your vehicle. Contact a mechanic or dealership to toll the vehicle. The mechanic needs to completely drain and flush the fuel system to get your vehicle back on the road.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

3 thoughts on “What Happens if you put Gas in a Diesel Engine?

  1. I put 18 litres of gas in my diesel tank by mistake. I then filled the tank completely with diesel, meaning that there was a mix of 72 diesel to 18 gas. The engine is a Mercedes 602.830 from 1999. Mercedes handbook states that you can add up to 30% gas and in very cold weather this will help. My engine ran perfectly well, I topped up with a further 10 litres of diesel after 100kmvto dilute the mix further. So not all diesel engines will suffer adversely with gas added.

  2. Hello Ron,

    I’m glad you figured out on time and removed the gasoline/diesel mixture on time.

    I’d recommend you use any of these diesel injector cleaners;

    Hot Shot’s Secret Diesel Extreme

    Peak “Blue” Agri-Clean Diesel Fuel Additive

    Lucas Oil 10013 Fuel Treatment

    Sta-Bil 22254 Diesel Fuel Stabilizer

    Power Service Products Diesel Kleen Plus Cetane Boost

  3. Hello Osuagwu.
    Last year during a cross country trip I mistakenly added gas to the fuel tank in my 2008 Chevy 3500 6.6 Duramax. I immediately took it to a dealer in N. Carolina who discovered my mistake and drained the tank saying he thought I would be OK and so far I have been. He suggested I use a fuel additive when I refuel to protect the high pressure injector pump and I’m not seeing anything in my search for guidance on what to look for in additive products to hopefully keep the pump from failing. I’m hoping you can advise me or offer an internet site where this is discussed.
    Fingers Crossed,

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts