What Happens If You Put Gas In A Diesel Engine – A Deadly Mistake?

Filling up your car is one of the easiest – and to my nose, the most pleasing – things you can do in life. Take the pump, slot your credit card in, jam the nozzle up your car, and start pumping. It’s not that easy to mess things up until that inevitable “Oh No!” moment appears as you just realised that you grabbed the wrong pump. So, what happens if you put gas in a diesel engine?

Well, isn’t this a [insert preferred curse word here] position to be in? As we switch to electrification and fuel cells, the vast majority of vehicles worldwide are still running on either gasoline or diesel. As such, this problem appears far more frequently than anyone would care to admit. Could those fuel mixtures be compatible with one another? Not really, no.

But what exactly happens as a result of this accident? On top of that, what can we do to solve it? Thankfully, there’s a fairly easy solution on the subject of what happens if you put gas in a diesel engine. However, you’ll need to act fast. Don’t panic, and don’t start your car! Not until you’re able to figure out what to do next, which we aim to help you out with.

• Gasoline v. Diesel
• Different Engines
• What Happens?
• What To Do Now?
• How To Fix It
• Conclusion

What Are The Differences Between Gasoline And Diesel?

Before we look at what happens if you put gas in a diesel engine, why is this a huge problem in the first place? Surely, if they’re both fuel that came from the same crude oil dug up from the ground, then it shouldn’t be a problem to mix them, right? Technically, that’s true, both gasoline and diesel share the same parent. However, they’ve been refined differently to give off unique characteristics.

• It has a thicker consistency and more viscous mixture than gasoline.
• Diesel is heavier (or denser) than gasoline, weighing in at one pound more per gallon compared to gasoline.
• It doesn’t evaporate at higher temperatures, while gasoline does.
• Diesel has some lubricating qualities, but gasoline doesn’t.
• It can self-ignite at lower temperatures compared to gasoline.
• Diesel engines don’t need spark plugs to ignite, while gasoline engines can’t combust without it.
• Diesel engines have a much higher compression ratio when compared to gasoline engines.

The last two points – concerning ignition and compression – is the most significant point of difference between gasoline and diesel engines. Consequently, this is where our problems begin when we look at what happens if you put gas in a diesel engine. In a nutshell, using either fuel in the wrong engine can create a lot of problems, all of which will be eye-wateringly expensive to fix if it’s not solved soon.

Gasoline is incompatible with diesel engines, and diesel is incompatible with gasoline engines. Diesel is far too thick and dense for a gas car’s fuel lines and fuel pump system. On the other hand, gasoline creates far too strong of an explosion when ignited for a diesel engine to handle. Either way, there are terrible consequences of running either fuel in an engine that’s designed for the other.

What About The Differences Between Gasoline And Diesel Engines?

Following along the point we made earlier, let’s take a technical turn at looking into what happens if you put gas in a diesel engine. So, just what separates the concept of ignition and compression with both gasoline and diesel engines. Well, both gasoline and diesel-powered engines follow the same concept of burning fuel to create power, which thus makes your car move.

However, there are major differences in how that combustion takes place. This will be important for us to learn more of what happens if you put gas in a diesel engine:

• Gasoline engines are considered internal combustion engines – or ICEs – as they burn fuel that flows into the engine. As gasoline rushes into the cylinders to be mixed in with the air, it gets ignited by the spark plugs. This controlled explosion forces the pistons down, which rotates the crankshaft. This, in turn, is where the power to move your car is generated.
• Diesel engines, meanwhile, are considered as compression ignition engines – or CIEs – though they’re similar. The key difference is that it relies on compression. Air is drawn into the combustion chamber and is compressed by the piston. This compressed and already hot air is further heated up by glow plugs (not spark plugs). Diesel is then injected and infused with super-hot air and is ignited.

In layman’s terms, gasoline is flammable, whereas diesel is combustible. While gasoline requires a spark to ignite, diesel – as it’s being compressed with intensely hot air – burns. The rest of the car’s energy generation process is otherwise similar. As we’ll soon find out as to what happens if you put gas in a diesel engine, that motor will bear the brunt of the damage.

What Happens If You Put Gas In A Diesel Engine?

Now, here comes the question, what happens if you put gas in a diesel engine? We’ve understood now the differences between these two mixtures of fuels. If you’ve got a sharp eye and spotted the problem before turning on your car, then there shouldn’t be an issue. We’ll explore more on that side of the matter in a bit. For now, what is the outcome if you’re completely blind to it?

You haven’t noticed that you’re pumping up the wrong gas, and are more than happy to keep calm and continue driving as nothing happened. What would the effects be in this scenario? Well, here are a few of the consequences of what happens if you put gas in a diesel engine, and proceed to keep on hauling.

Whether you’re knee-deep in this situation right now, are preparing for a possible encounter, or are just curious, it’s time to pay attention:

Outcome 1 – There’s No Ignition, And Your Car Won’t Crank Over

The first, and perhaps most noticeable reaction of what happens if you put gas in a diesel engine is the possibility that it won’t start. Or, it may have trouble at first, but will eventually turn over. The explanation for this is quite simple, and we’ll have to delve into the chemical make-up of gasoline.

Gasoline – or petrol, as they call it outside of the US-of-A – is chemically engineered so that it won’t ignite automatically. At the very least, it won’t ignite so easily without the right set of circumstances at play. This being a timely burst of electric charge from the spark plugs.

Within a glow plug-equipped diesel engine, however, gasoline simply can’t ignite. Should your car have some remnants of diesel in there that’s been mixed with the gasoline, it will start. That said, what damage you’ve caused here is significant enough to warrant serious repairs.

Outcome 2 – Black Plumes Of Smoke Coming From The Exhaust

More on alchemy, we have to talk about ‘flashpoint‘, or the minimum temperature required for a compound to ignite. Diesel fuels have a flashpoint of between 126 and 205 °F (or 52 and 96 °C). A gasoline mix, meanwhile, has a flashpoint of around −45 °F (or −43 °C).

You might think this means gasoline is easier to ignite, but that’s not really the case. We also have to look at ‘preignition’, or a premature ignition caused by residual heat. To ensure this doesn’t happen, fuels need to also be designed with a specific ‘autoignition’ temperature in mind.

When we look at it this way, gasoline has a much higher autoignition temperature, at around 536 °F (or 280 °C). Diesel, on the other hand, sits at 410 °F (or 210 °C). Combined, we can say that gasoline will have a tough time while trying to ignite inside a diesel engine.

This is because a diesel engine can’t provide the high temperatures needed to light up the gasoline. Although it may eventually ignite, there’ll be a lot of excess and unburnt fuel left behind. This forms soot, which comes out of your exhaust as thick plumes of black smoke.

Outcome 3 – There’ll Be No Lubrication Inside The Engine

Another one of the chemical differences between diesel and gasoline is how they behave once inside your engine. Diesel, as we learned earlier, has some lubricating properties, which makes it similar to motor oil in a sense. Its gasoline counterpart, nevertheless, is engineered more like a solvent.

As a diesel engine is designed to have diesel flowing in them, it’s consequently made to operate with these lubricating abilities in mind. You can imagine what happens without it, as the engine is filled to the brim with gasoline.

First and foremost, much of the diesel engine will be starved of any lubrication. Soon, the engine will be contaminated with gasoline. Without lubrication, the engine’s many internal moving parts would rub, grind, and contact each other. This leads only to irreversible engine damage.

Outcome 4 – Extensive Damage To The Fuel System

Remember how we mentioned that diesel is thicker than gasoline? This comes back to haunt us, as pumping up your diesel motor with gasoline has adverse effects on the fuel system. The parts that feed the engine with diesel are tuned for the more viscous and denser diesel, not gasoline.

The latter mixture of fuel is much thinner and lighter. Should there be gasoline flowing around rather than diesel, your diesel engine’s fuel injectors, fuel pump, fuel lines, and fuel filter will suffer intense wear. Quickly, they’ll fail one by one and will have to be replaced.

Outcome 5 – The Engine And Its Internals Will Suffer Irreparable Damage

Your engine, be it gasoline or diesel, has countless moving parts. Among those most exposed directly to the combustion process are the components that create reciprocating motion. Reciprocating can be defined as the up and down rotations that translate explosions into movement.

These parts include the pistons, connecting rods, and wrist pins. Although, as we hinted before, gas can’t ignite easily inside a diesel engine, it could eventually ignite. Unfortunately, the combustion of gasoline is quite a bit more powerful than diesel’s more (relatively speaking) gentle compression.

Diesel engines, therefore, aren’t built to handle the forces of gasoline detonation. This excess shock is more than capable to damage or break those aforementioned reciprocating components. When combined with everything else, the rest of the engine is destined for junk, as well.

What Happens If You Put Gas In A Diesel Engine – What To Do Now?

We all have our little accidents now and then. So far, the topic of what happens if you put gas in a diesel engine happens to way more people than we’d readily admit. The most important thing to do is that we recognize these mistakes, and act fast to resolve them. If you’re lucky, you’d snap back to realize that you’re putting the wrong fuel while you’re still at the pump.

Should that be the case, then you have a chance of saving your engine. In fact, it’s quite rare to see any diesel-powered vehicle be damaged catastrophically by gasoline infusion… So long as you spot the mistake and follow these steps down below. What happens if you put gas in a diesel engine is never good. But be alert, act swiftly, and you shouldn’t have to pay the repercussions.

Step 1 – Don’t Turn On Your Vehicle

Pumping gasoline into a diesel-native vehicle isn’t the contributor to those side effects that we’ve nagged you about earlier. However, turning your vehicle on and letting that gasoline ignite (or try to ignite) is most certainly the source of misery.

If you realised that you pumped gasoline into your diesel car, then don’t turn it on. Merely trying to crank it over is sufficient to result in damage. So, don’t even attempt to switch on the ignition and drive down to the local mechanics a block away.

Instead, call a tow truck, and don’t touch the ignition until the gasoline’s all flushed out. Alas, most folks only realize that there’s a problem after they’ve cranked the engine. Should this be you, then turn your engine back off immediately. At least now, you’ve limited the extent of the damage.

Step 2 – Head To A Mechanic As Soon As Possible

When we mean “head”, we meant with a tow truck, and we can’t emphasize this enough. Head over to a nearby mechanic at once, and the sooner the better. Keep the gasoline in there for long, and it’ll start to contaminate the rest of the system.

Once you’ve reached the mechanic, they can begin to flush and drain out the system of any gasoline. Some folk may tell you that you can save a few pennies if you flush out the gasoline at home. Unless you have the right equipment, skills, and experience, we don’t recommend this.

It’s simply because the gasoline needs to be thoroughly drained of every drop. It’s crucial that you have a professional handle this. Even 1% worth of gasoline contamination could drop the diesel’s flashpoint by around 64 °F (or 18 °C).

Step 3 – Have The Local Technicians Drain Your Car

At this point, the mechanic will start draining your car of every single molecule of gasoline. If there’s an opportunity, we’d probably recommend sending your affected vehicle over to a specialist. They know their way around diesel engines and could get this draining job done rather quickly.

But once again, haste is far more important, so practically any workshop will do. In any case, all the work required for drainage shouldn’t be too expensive, nor should it take too long. If you’ve already tried cranking your vehicle at the station earlier, then be sure to let your mechanic know.

In the meantime, they’ll check over the engine, fuel injectors, and fuel pumps to see if there’s any residual damage. As for the price, a typical drainage job like this should cost somewhere around $200 to $500. It’ll vary depending on how far the gasoline’s gotten into the system.

There’s a good reason why spoke about the rapidity of your response, and that has to do with the price of repairs. If you put off immediate drainage, the gasoline could’ve traveled deep into the fuel lines or engine. Doing so could rack the costs up in the neighborhood of $1,500 to $2,000.

What Happens If You Put Gas In A Diesel Engine – How Do You Fix This?

We spoke a lot about draining it earlier once you’ve asked yourself as to what happens if you put gas in a diesel engine. So, what entails in a drain? Well, approximately one in seven people have at some point in their life mis-fuelled at the pump. Overall, the process of pumping out the gasoline has, as it seems, been quite familiar. How much of a fix it requires depends on five key factors:

1. How much gasoline did you accidentally pump into your diesel car?
2. Is there at least some diesel left in the tank before you filled in the gasoline?
3. Did you, or did you not attempt to start up the vehicle after you’ve filled it with gasoline?
4. Have you driven the vehicle long and far enough to notice engine troubles?
5. Did you keep on driving until your car gave up on you and stalled?

Irrespective of what happens, there are common troubleshooting steps shared among them. For you who’s asking what happens if you put gas in a diesel engine, this is how you fix it. It might be good of you to understand this, as it could allow you to understand what your mechanic has to go through to solve this:

A (Simplified) Step-By-Step Guide To Solve What Happens If You Put Gas In A Diesel Engine

1. The first step would likely require dropping the tank. In other words, detaching your car’s fuel tank. If you haven’t cranked the engine yet, then the damage will most likely be isolated inside the tank.
2. Once it’s been removed, the mechanics can start to drain out the tank. In older vehicles, draining the tank alone almost always helps to solve the issue. However, modern vehicles have more advanced fuel injection tech that necessitates more detailed draining.
3. The fuel pump is the next component to look at. Have your mechanic buddy inspect this, and see if it needs a replacement. If you’re quick and haven’t yet tried to start your car, the fuel pump could be spared. Still, you may consider a replacement for peace of mind.
4. Next up, you’ll have to remove and drain out the fuel lines. They’re generally quite robust, and won’t wear too easily with gasoline contamination. Nonetheless, they should be fully flushed and cleaned, just to make sure.
5. Most technicians will recommend that you swap out the fuel filter after a misfuelling incident. Even if just a tiny bit of gasoline got stuck there, the contamination would spread. While you’re at it, clean out the fuel filter reservoir, too.
6. Should the engine not yet see any gasoline intrusion, you’ll then have to check the fuel rails and fuel injectors. The rails could easily be cleaned. Although, and if the damage is too severe, you’ll need to have these replaced, as well. As for the diesel injectors, you’ll need to think about repairing them if the damage is relatively light. Otherwise, only a replacement will suffice.

What Happens If You Put Gas In A Diesel Engine – Prevention And Conclusion

Whether it’s diesel in a gas car, or gas in a diesel car, the results are the opposite of ideal. On the bright side, it’s much harder to get them mixed up these days. Most fuel stations use different styles of nozzles for both gasoline and diesel. The nozzle on a diesel pump is larger than that of a gasoline one. As a result, a diesel pump nozzle may not fit through the filler port of a gasoline car.

Unfortunately, a gasoline pump’s nozzle is small enough in diameter, that your diesel car’s filled has no problem accommodating it. This is where the issue lies, as you wonder about what happens if you put gas in a diesel engine. In all, our only recommendation is to be prudent when you pull up next to the pump next time. Observe, most especially, the color of the pump and its handle.

In the US, diesel pumps are typically green, while gasoline pumps are black. If you find yourself in a position where the gasoline has already trickled in, then act fast. Don’t start your car, and have it sent to a workshop to have the gasoline drained. If not, you’ll pay quite a lofty price to get it all fixed and running again. It’s an honest mistake, but it’s utterly deadly if you don’t solve it in time.

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