What To Put in Gas Tank To Ruin an Engine

The internal combustion engine is one of the most complicated mechanical systems we encounter every day. And at the heart of an engine are moving parts which are assembled with utmost precision and tolerances of one ten-thousandth of an inch. So, it doesn’t surprise that putting anything other than the fuel an engine is designed to run on will cause at least some damage.

But we are not here to discuss some damage; we are here to learn what to put in a gas tank to ruin an engine entirely and quickly. Well, there are several substances that will do the job, some of which are sugar, water, and Coca-Cola. You will also achieve roughly the same results with oxidizing agents such as bleach and hydrogen peroxide.

So, stick around as we dive into more detail on each substance, after which you can decide for yourself which one is best for the goals you are trying to achieve.

what can you put in a gas tank to ruin the engine

What To Put in a Gas Tank To Ruin an Engine


Putting sugar in a gas tank is a method best reserved for direct injection engines. That’s virtually all diesel engines after 2000 and all gasoline engines after roughly 2015. And the reason that works is because sugar isn’t soluble in gasoline. And contrary to what some people believe, the fuel filter won’t stop sugar, meaning it will end up in the fuel system and the engine.

However, the engine itself isn’t the main target here; the direct injection high-pressure fuel pump is. The high-pressure fuel pump is an extremely sensitive part with moving components inside, and if we introduce sugar into it, the sugar will grind off those internal components. What happens after that is tiny metal shavings, almost microscopic, will end up in the entire fuel system.

But before that, the fuel pump will fail in a matter of 15-20 minutes of driving which is a $600-$800 repair by itself. However, once you install a new fuel pump, those tiny metal shavings that are now in the fuel system will destroy the new fuel pump as well in a matter of days at most.

So, the only way you can properly solve this problem is to remove the entire fuel system, including all the fuel lines, fuel pumps, fuel rail, injectors, etc. And thoroughly clean them, but even then, chances of small debris remaining in the system are present. So, ultimately, sugar in a gas tank will end up being a $1,500 repair bill at the very least, but it’s more likely it will be closer to $2,500-$3,500.


Here is what to put in a gas tank to ruin an engine entirely, water. Although water is highly corrosive, that’s not the reason why putting it in a gas tank will ruin an engine. You see, the engine is essentially a piston air pump, and the job of those pistons is to compress the air-fuel mixture inside the combustion chamber. And that’s great because the atomized fuel and air are compressible. Water, however, isn’t. When water enters cylinders, because the car was flooded, for example, they won’t be able to turn over. Again, that’s because water cannot be compressed.

Now, if you put water in the gas tank, you will be able to start the car because the water still hasn’t reached the engine. But once the water enters a running engine, the pistons will hit it and lock up. But since they have been moving at ridiculous speeds, the engine won’t simply stall. Instead, the pistons will crack, the connecting rods will bend, the crankshaft might break, etc. And all that means is that the engine will be totaled in a matter of minutes.


Bleach is the first oxidizing agent on this list. Now, bleach might not be the best oxidizer, but it will do the job well enough, and what oxidizers do is speed up metal oxidation. In other words, make metal rust or corrode faster. And the fact that metal rusts much faster when it heats up will help bleach even more. And although bleach in gas tank will take more time to ruin an engine than sugar or water, the whole process still won’t last longer than 15-20 minutes of driving.

And once bleach reaches the combustion chamber, the cylinders, pistons, valves, and all other moving components it reaches will rust and seize up. That means the engine seizes up and thus is completely totaled. After that, there is virtually no component that can be salvaged, and the entire engine will end up in a scrap yard.

Coca Cola

Coca-Cola is another readily available liquid you can put in a gas tank to cause trouble for someone. However, Coca-Cola won’t ruin an engine and works only if you want to inconvenience someone and give them huge repair bills. That’s because Coke won’t lock up an engine, it won’t speed up oxidation, and it won’t destroy the fuel pump the same way sugar will. But even so, Coke will sludge up the entire fuel system, and it will do so after only 10-15 minutes of driving, thus leaving the driver stranded.

And once the car is towed to a repair shop, the technicians likely won’t clear the Coke out of all components. Instead, they will want you to buy a new fuel pump, fuel rail, and new injectors. All that will cost upwards of $1,000, plus they still have to clear the rest of the system, which will add another $500 at least. And on top of everything, the whole job will take at least two to three days by the time all the parts are sourced, and all the work is done.

Hydrogen Peroxide

We already discussed what bleach will do to an engine because of its oxidizing properties. Well, if you really want to make sure the engine is ruined and leaves no place for error, then you should use hydrogen peroxide. Hydrogen peroxide is also the answer if you want to know how to ruin a car engine fast. That’s because hydrogen peroxide is the best oxidizer on this list and will do the job of seizing the engine the most efficiently. Plus, you can buy hydrogen peroxide at all pharmacies as well as in all bigger market chains like Walmart.

And just to mention once again, hydrogen peroxide in a gas tank will cause the internal engine components (cylinders, pistons, valves) to corrode at an alarming pace and seize the engine in 15-20 minutes. That means catastrophic engine damage and a repair bill of whatever a new engine costs, plus $1,000 to $1,500 for labor.

what to put in gas to ruin engine

How To Ruin an Engine Without Evidence

If you want to destroy an engine without evidence, only a couple of the previously mentioned methods will work. For example, Coke will leave a lot of sludge traces, and it will be pretty obvious what happened. The same goes for sugar which will remain virtually the same crystallized shape you put in the gas tank. Furthermore, hydrogen peroxide will leave some traces too in the shape of white foam.

However, water and bleach are the answer to how to ruin an engine without evidence because they likely won’t leave any traces behind. For example, water will leave a hole in the piston, after which it will fall through into the motor oil. And since the engine is completely ruined, even the most experienced mechanic will just assume the head gasket had a massive leak. As for bleach, weird traces might remain, but unless the driver suspects something, it’s highly unlikely anyone will assume the engine was sabotaged. Plus, the first thing the technician will check is if the engine turns over, and once he finds it’s seized, there is no need to disassemble it because he will already know that it’s irreparable.

How To Prevent Engine Being Ruined

Unfortunately, there aren’t many ways you can prevent someone from sabotaging your car because sooner or later, it will be parked somewhere accessible. However, some of the things you can do to minimize the chance of that happening are to, first and foremost, be careful where you park the car.

For example, if at all possible, always park it in a closed garage. And if that’s not an option, park it somewhere crowded and with a lot of traffic. At night, make sure the car is well-lit, and again, make sure it’s on a high-traffic street. Plus, needless to say, make sure the car and the fuel cap or cover are always locked, and inspect the fuel cap cover every morning for any signs of damage or that someone tried to open it by force.

As for the more advanced methods, you can always buy a vehicle security camera. You can find them on Amazon for around 30 bucks; they film in HD and are wireless. Plus, they provide a live feed or recording. That way, you can quickly review the recording in the morning, and if someone did sabotage your car, the HD camera will increase your chances of finding the culprit.

Frequently Asked Questions – FAQs

Q: Will Putting Water in a Gas Tank Ruin an Engine?

Yes, putting water in a gas tank will ruin an engine. Once the water reaches the combustion chamber, the pistons will most likely crack because water cannot be compressed. Other than the water punching a hole in the pistons, the connecting rods will likely bend, and the total damage will be in the thousands.

Q: What Happens if You Put Cooking Oil in a Gas Tank?

Putting a certain amount of used cooking oil in a gas tank of an older diesel vehicle most likely won’t cause any damage, and in some cases, the engine will run just as well as it does on diesel. However, newer diesel engines, and especially all gasoline engines, will sputter and ultimately stall. But again, no damage other than having to clear the fuel system will be caused.

Q: What Damages an Engine the Most?

The most damage an engine can experience, and the fastest, is by running it without oil. Running an engine without oil will absolutely destroy every single moving component inside it, from the bottom end, the pistons, and cylinders to the valve train. All that damage is irreversible and will happen in a matter of half a minute.

Q: What Happens if You Put Water in Oil Tank?

If you put water in an oil tank, the motor oil will sludge up, become too thick and stop circulating. That leads to an oil pressure drop, plus the oil loses all its lubrication properties which means that catastrophic engine failure will occur in a matter of minutes. However, a small amount of water won’t cause extensive damage immediately, although the risk is high.

Q: How Long Does it Take For Water To Mess up a Car?

If you put water in the gas tank, it will take about ten to fifteen minutes to mess up the car. In other words, as soon as it reaches the engine from the gas tank. However, if the car is sitting in water, the extent of damage depends on the water height. But as soon as it reaches a certain electrical component or a control module, it will require cleaning unless it has power when the water reaches it, in which case it will probably fail immediately.

Q: How Does Salt Water Affect Cars?

Saltwater is ten times worse for a car than normal water. First of all, salt water is much more corrosive which will destroy all the metal components much quicker. Secondly, salt water is much more conductive, which increases the chances of electrical shorts exponentially, especially if it reaches a control module.

Q: How Long Does Salt Take To Damage a Car?

The problem with salt water is that even when it dries up, the salt remains. In turn, the car will begin rusting immediately, and if the water gets into the cylinders, the engine will seize up in a matter of one day. Furthermore, all electronics touched by salt water will be immediately shorted and destroyed.


Ultimately, putting anything other than the correct fuel in a gas tank will eventually cause some damage. However, if you want to destroy it in the quickest and most efficient way possible, then choosing one of the substances and fluids on our list is the way to go. So, if you don’t want to leave any or minimal traces behind, use bleach or water. But if the evidence is not a concern, sugar or hydrogen peroxide will do. And lastly, if you want your actions to only result in a high repair bill instead of destroying the engine, you can use Coca-Cola.

Ibro Cehic

Ever since I was bitten by the automotive bug during early childhood I was obsessed with cars. My first driving experience came when I was ten and I already started tinkering with cars and motorcycles at thirteen. So, right from the beginning, I knew my life would revolve around cars, even if I wasn’t sure how that would happen. And today, thanks to my second passion, writing, I get to share my love for automobiles with other enthusiasts through my articles.

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