What Happens If You Put Gas in a Diesel Truck? A Detailed Explanation

Have you ever pondered the question, “What happens if you put gas in a diesel truck?” This is a legitimate concern, especially for those who own both diesel and gasoline vehicles. The risk of inadvertently filling up at the wrong pump and introducing the incorrect fuel into the tank is real. In this article, we will explore the consequences of using gasoline in a diesel engine and provide advice on what to do if this happens.


Diesel vs. Gasoline Engines: The Key Differences

Both diesel and gasoline engines are types of internal combustion engines. They burn fuel to generate the force that propels your vehicle. However, diesel engines combust fuel under high pressure. The high pressure and temperature cause the diesel fuel to ignite without needing a spark plug, unlike gasoline which is thinner and requires a spark for ignition.

Diesel fuel serves a dual purpose: it acts as an energy source and a lubricant. Diesel engines depend on the lubricating properties of diesel fuel for the fuel injector and other fuel system components. These physical differences influence how the fuel behaves in the combustion chamber.

The Impact of Gasoline on a Diesel Engine

The amount of gasoline introduced into a diesel engine significantly impacts the level of damage. A full gasoline tank will cause more harm than a few gallons of gasoline mixed with diesel fuel. A gasoline-diesel fuel mixture ignites more readily, which could lead to premature ignition within the engine. This uncontrolled and untimely detonation within the engine is akin to a small explosion. The diesel engine, not designed to handle this, will sustain damage.

If the engine runs at all, it’s likely to stutter. The gasoline will not ignite consistently due to the absence of a spark plug, and the fuel will not burn correctly, resulting in black smoke from the exhaust. The fuel pump and fuel injectors may fail due to gasoline’s inability to function as a lubricant.

Eventually, the engine will stop running entirely, necessitating substantial repair or replacement. Naturally, you’ll want to avoid this disastrous scenario.

What to Do If You Misfuel?

The best course of action, if you add gasoline to a diesel engine, is not to start it. Arrange for the vehicle to be towed to a professional auto repair service to drain the diesel tank. If you’ve already started the engine, stop it immediately and have the vehicle towed for fuel drainage.

Damage to the fuel injector may be irreversible. However, a professional mechanic can determine which engine parts can be salvaged and rebuild the engine. If you put gas in a diesel truck, you’ll likely need a new engine or at least significant engine repair.

How to Prevent Misfuelling Mishaps in the Future

Given the severe consequences of adding even a small amount of gasoline to a diesel engine, finding ways to remind yourself which fuel to use when you’re at the pump is crucial. Here are some tips to help you avoid misfuelling:

  • Always check the label on your fuel cap. It should clearly state “DIESEL ONLY.” If it doesn’t, consider adding a warning sticker.
  • Use color-coded labels for the fuel caps of your diesel and gasoline vehicles.
  • Match your key rings to the color of the fuel caps. This will serve as a final reminder before you turn the key.
  • When at the pump, familiarize yourself with the differences between diesel and gasoline pumps. This will help you ensure you’re at the correct pump and provide a final check as you insert the pump before you start fueling.

Repairing the Engine System After Misfuelling

Once your vehicle is at the repair shop, the mechanic will drain and clean the tank, replace the filters, and inspect other components, such as the fuel injectors and the fuel pump. If you didn’t start the vehicle after misfuelling, there’s a higher chance that more engine components could be spared from damage.

Professional Engine Repair After Misfuelling

In the end, if you put gas in a diesel truck, you’ll find yourself at an auto repair shop. You need a trustworthy mechanic to rebuild your engine after a misfuelling incident. Experience can make the difference between spending thousands on a rebuilt engine and spending much less on a few replacement parts.


Misfuelling a diesel engine with gasoline can lead to severe damage and costly repairs. However, with the right precautions and immediate action if misfuelling occurs, you can mitigate the damage and keep your diesel truck running smoothly. Always double-check the fuel type before filling up, and if you make a mistake, don’t start the engine and seek professional help immediately.

About the author, Laurence Perkins

Laurence Perkins is the passionate car enthusiast behind the blog My Auto Machine. With over a decade of experience in the automotive industry, Perkins has knowledge and experience with a wide range of car makes and models. His particular interests lie in performance and modification, and his blog covers these topics in-depth. In addition to his own blog, Perkins is a respected voice in the automotive community and writes for various automotive publications. His insights and opinions on cars are highly sought-after.