What Happens if You Put Diesel in a Gas Car?

Have you been caught off-guard and without paying attention pulled up to the wrong pump? What matters most is what you do next.

Maybe you are distracted or not thinking. You pull the diesel nozzle out of the pump instead of the gas nozzle and start filling your tank. Most people realize their error before the dirty deed is done, but not everyone is that lucky!

So what happens if you put diesel in a gas car? It’s not the horror story that some people like to spread that your car will be permanently damaged. As long as you take the necessary steps immediately you realize your mistake of putting diesel into your gas tank then you can save the day.

What Happens If You Put Diesel in a Gas Car?

First of all, let us understand the difference between Gas and Diesel. Although they are both made of the same chemicals, there are some differences.


  • Diesel is distilled from crude oil and has a thicker consistency and viscosity
  • Diesel uses pressure and compression to ignite itself therefore, diesel engines do not have spark plugs.
  • Because of its thicker consistency and depending on the time diesel is left in the engine, it can cause blockages in the fuel injectors, filters, and gas


  • Gas is also derived from crude oil but has a much thinner consistency
  • Since gas is combustible and can ignite by itself often chemicals are added to it. Ethanol is a common additive to gasoline
  • Gas engines use spark plugs to ignite the fuel and air to spark

When diesel does accidentally end up in a gas tank it is not the end of the world.

The car will start of course, because some gasoline remains in the fuel line and this will allow the car to drive for a short distance until this gasoline gets consumed. The vehicle may misfire and if this goes on, smoke will start coming out of the exhaust.

The car will slow down and eventually, it will just come to a stop. 

What to Do When This Happens

So what to do when you do accidentally put diesel into a gas tank?

The steps you take to right the wrong can differ depending on the amount of diesel that has been mixed with the gas.

Fill the Tank With Gas

The solution, if you have only put a small amount of diesel into your gas tank, is simply to fill the tank up.  

Most engines can survive this mistake when there is only about 10 percent contamination of diesel in your fuel system. 

Call a Towage Service

If you have left the petrol station and have realized your mistake while driving to your destination take these steps.

  • Immediately pull over and stop your car in a safe place
  • Switch the engine off
  • Disconnect the battery
  • Call a towage service and have the car towed either back home or to your mechanic of choice. 

Most people are not equipped to deal with this situation themselves therefore it is advisable to have the car towed to your mechanic who can then attend to this problem quickly and appropriately. 

Drainage of The Fuel System

The next stage is to drain the fuel system. You have to start by emptying the gas tank. Using a siphon to remove the diesel. Then what is needed is to clean the diesel fuel out of the fuel lines and the injectors.

If you are lucky, sometimes, when completing this step and the fuel system is cleaned of any diesel will fix the problem. This of course can depend on the amount of diesel still left and the amount of time the diesel has been left in the fuel system.

You are now ready to start the engine. This may take several attempts as there are still some remains of diesel in the engine.

You will notice a lot of smoke coming out of the car’s exhaust and there may be some smell as well.  Don’t panic this will continue to happen until all the diesel works itself out of the fuel system.

Get Professional Help

Most people are not mechanically proficient and the most DIY work they have done on a car is filling the water cooler!

In this case, the easiest and safest solution is to call a professional mechanic. A mechanic will properly flush and clean out the fuel system.

In some cases depending on the amount of time diesel stands in the fuel system, relevant car parts like injectors, filters, and spark plugs will be replaced.

Can You Prevent Misfuelling?

Keep in mind that putting diesel into your gas tank occurs far fewer times than the other way round. There is a very simple reason, this being, that the nozzles differ.  A diesel nozzle is much bigger than a petrol nozzle tank opening.  

However, there are times when this is still possible.  In today’s busy world one can get easily distracted as your mind is on other things.

There are many ways to try and prevent making this mistake.

  • You could be unaccustomed to filling up your tank. Should the nozzle not fit in easily, don’t force it to take this as a wake-up call that you are actually trying to fill with the wrong fuel
  • You could be in a strange or new car and are not sure of which fuel to use. Most petrol attendants can help you with this or most caps indicate which type of fuel the vehicle uses
  • Pay attention to the sticker on the fuel pump as it will indicate what type of fuel you are pumping

Do Not Panic if You Put Diesel Into Your Gas Car

If you by chance put diesel into your gas tank, do not panic! 

If you follow the steps stated above your engine will survive, and you will be on the road again in no time at all.

Call the experts and they will help you with your misfuelling error with professional and speedy assistance.

I hope this article helps you understand what happens if you put diesel in a gas car. 

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