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What Happens If You Put Diesel in a Petrol Car?

  • Author :
  • TATA AIG Team
  • Published on :
  • 07/02/2023

Filling your tank with the incorrect type of fuel is a regular and honest error. However, it is uncommon to load diesel engine oil in petrol cars. The fundamental reason is that petrol four-wheelers have an edge in terms of refilling nozzle size. The nozzle of the diesel dispenser does not fit into the tank of a petrol four-wheeler because the aperture is smaller. On the other hand, misfuelling a diesel-powered four-wheeler is easier and more prevalent. But what happens if you accidentally put diesel in a petrol car or petrol-powered car with diesel?

Why It’s Important to Avoid Putting Diesel in a Petrol Car?

The main issue is with the engines' functioning system. Diesel engines utilise fuel to lubricate internal engine elements, which poses a significant difficulty. According to the mechanism, fuel gushes into the interior elements of the diesel engine. Furthermore, because fuel has no lubricating capability, it will severely harm the engine.

If you want to know more about what happens after putting diesel in a petrol car, this blog is exclusively penned for you to avoid future mistakes. But do you know, just like putting the wrong fuel into your car can create serious consequences, not having car insurance in India has severe consequences?

Under the 2019 Motor Vehicles Act, a car owner is required to drive with a car insurance policy. A four-wheeler insurance coverage shields you from potential financial risks such as theft, accidents, and damage. As a result, you must get insurance for four-wheelers that will financially protect your car from losses.

Also, if you are discovered driving without four-wheeler insurance, you'll face a fine. A fine of ₹2,000, imprisonment for a maximum of 3 months, and penalties under Indian law. The prior provision cost ₹1,000 for driving without motor insurance. If you repeat the same offence, you'll be charged a fine of ₹4,000, together with 3 months in prison, at the discretion of the law. As a result, any cars that are not covered by a car insurance policy will be fined.

Now, moving on to the main section of the blog regarding what happens if diesel is filled in petrol cars. Continue reading to learn more.

What Are the Repercussions of Misfuelling?

Regardless of the possibility of misfuelling, both instances (diesel filled in petrol cars or petrol in a diesel-powered car) might cause engine damage. Consider the following situations:

Scene 1: Diesel Filled in Petrol Cars

Because the nozzle of a petrol four-wheeler tank is smaller than the nozzle of a diesel distributor, the risks of misfuelling are greatly reduced. However, the possibilities of harm are quite low if a petrol-powered four-wheeler is topped up with diesel. Because petrol is considerably more refined than diesel, it is ignited by the spark produced by spark plugs.

When a petrol-powered four-wheeler is started with diesel in its tank, the diesel clogs the fuel system and the spark plugs. The car's fuel filter is one of the first components to be harmed since petrol engine fuel filters aren't used to the oily nature of diesel. These will cause the engine to misfire, produce exhaust smoke, and perhaps cause the car to stall.

Scene 2: Petrol Filled in Diesel Cars

This is an unfortunate mistake that could result in extensive engine damage. Misfuelling a diesel four-wheeler becomes easier as the nozzles on petrol dispensers become smaller. Unlike petrol-powered engines, diesel-powered engines compress the fuel to ignite it, forcing it into the engine's internal components to lubricate it. The issue begins here.

It is difficult to eliminate the fuel that circulates in the diesel engine's fundamental elements. The lubricating quality of diesel is critical to the correct operation of the fuel injection pump. Because petrol is incapable of performing that function, the performance becomes uneven. The worst thing is that misfuelling in diesel four-wheelers takes some time to notice, and by the time you notice the mistake, the car will be spewing out black fumes from the exhaust pipe, moving slowly and eventually stopping.

What Can You Do If You Put the Incorrect Fuel In Your Car?

It is critical to address a misfuelling problem as soon as you become aware of it. Here's what you may do in each of the cases stated above.

Diesel Filled in Petrol Cars

As previously said, the first situation is not as bad as the second. So, if you've topped up your petrol-powered four-wheeler with diesel, you may take the following precautions to guarantee that you do not suffer as a result:

If You Notice When Filling Up: If less than 5% of your car's tank capacity is filled with diesel, you may fill the rest with petrol and drive properly. Diesel easily blends with petrol. Thus, there should be no issues in this scenario. However, it is advised that the fuel be completely drained to avoid any contamination.

Realising After Filling It Up: The problem is still under control. It is critical not to start the engine if more than 5% of the tank's capacity is filled with diesel. Instead, you may contact a tow truck and have the four-wheeler towed to a nearby repair shop. Completely drain the diesel and cleanse the fuel tank. Once the tank is empty and fully cleansed, you may refill it with petrol, and your four-wheeler will be ready to drive.

If You Have Started Your Engine: If you have started your engine, switch it off as soon as you realise it. Drain the fuel tank completely and carefully cleanse it and the fuel line with clean petrol. Once the process is complete, you may fill up your four-wheeler with petrol and drive away without more complications.

If You've Been Driving for a While before Realising: This is the worst-case situation. Stop your vehicle as quickly as possible and switch off the engine. You might try contacting a roadside assistance or towing agency to have your vehicle towed to the nearest worksite. Have your car's tank and fuel lines cleaned off the tainted fuel. Once the cleaning is done, you may refuel your four-wheeler. Ideally, there should not be any problem after a thorough cleaning, and you may continue driving without problems. However, as a precaution, you should change your fuel filter as soon as possible.

Petrol Filled in Diesel Cars

Diesel-powered four-wheelers are not as forgiving as petrol-powered vehicles. If you start the engine with improper fuel in the tank, you will almost certainly wind up with a large charge. The main reason for this is that when the engine is started, fuel gushes into the engine's internal parts, which require lubrication to function correctly. If you accidentally fill up your diesel car with petrol, here's what you can do:

  • Don't Switch On the Engine: Whatever occurs if you discover that your diesel vehicle has the incorrect fuel in its tank, don't start the engine. Your four-wheeler is safe as long as the petrol is in the tank and the engine is not switched on. Tow your four-wheeler to the nearest workplace and have the tank drained with the help of a skilled technician. After flushing the tank and main fuel line, you may refuel your four-wheeler with diesel and consider adding an additive in order to clean the injectors.

  • Remember: Four-wheelers with automatic transmissions will continue to pump oil into the system even if the key is turned to the ignition slot to move the vehicle into neutral.

  • If You Drove the Four-Wheeler for a While before Realising: This may be the most disastrous scenario. If you have driven your diesel-powered four-wheeler with petrol in the tank for an extended length of time, the petrol has most certainly been pushed to every area of the engine.

As soon as you realise your error, stop your car and switch off the engine, and contact roadside assistance or towing service to transport your vehicle to the nearest authorised service centre. Hire a professional to work on your vehicle. The bill you would have to pay in this situation would be determined by the level of engine damage.


As previously said, this error is more prevalent than you may assume. It's all too easy to go into autopilot mode when you're sleepy or preoccupied. And when you perform something as mundane as topping up fuel on autopilot, you may unintentionally put the incorrect fuel into your four-wheeler.

Whenever you work on your four-wheeler, whether driving it or fixing it, you must be completely focused. When you allow your focus to stray, accidents occur. So, could you make it a point never to refuel while you're tired? Do it at the beginning of your travels rather than the finish, when you feel as energised as you can be. You might also place a little sticker near your fuel cap to remind you of the type of fuel your vehicle requires.

And, if you truly want to protect yourself from such costly errors, you may invest in Tata AIG's comprehensive car insurance policy with specific add-ons that you feel you might require. You can take the assistance of our online car insurance calculator to learn about the premium rates of your policy and make a wise decision based on your requirements and budget. Contact us if you require any kind of help! We would be happy to assist you!

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