What Happens if You Put Gasoline in a Diesel Engine?

If you own a vehicle, you likely know the basics of taking care of it. While you may know the kind of fuel it requires, we also know how easy it is to make a mistake. Maybe someday, you accidentally happen to put gasoline in a diesel engine and think that it’s not a big deal.

The truth is, you just might turn your car into a useless pile of scrap metal. Let’s take a look at why gasoline in a diesel engine might spell disaster for your vehicle.

How are Gasoline and Diesel so Different?

diesel fuel pump

Both gasoline and diesel engines are internal combustion engines designed to turn chemical energy (fuel) into mechanical energy. This mechanical energy moves pistons that are connected to a crankshaft. This linear motion results in a rotary motion that moves the vehicle.

As we mentioned, diesel and gasoline are powered through small combustions. The major way these engines differ is how the fuel is combusted. While diesel and gasoline both come from crude oil, diesel is refined to be heavier meaning it doesn’t need a spark plug to ignite.

In a gasoline engine, the fuel is mixed with air and compressed by pistons. The fuel is then ignited by spark plugs.

In a diesel engine, the air is compressed, and the fuel is injected. When air is compressed it heats up and the fuel can then ignite.

Ignition Temperature

The minimum temperature required (flashpoint) to ignite fuel in a diesel engine is 52 degrees Celsius. In a gasoline engine, it’s a whopping -43 degrees Celsius. You might already see what the problem is here.

The gasoline is going to have a much harder time igniting. This means it’s going to build up in the cylinders. Granted, it can ignite but most likely at the incorrect time.

Injection/Lubricity Problems

Diesel injectors are calibrated to spray diesel fuel into a fine mist, not gasoline which is less dense than diesel. Consequently, these injectors also run at higher pressures in comparison to gasoline injectors. This can easily blow out a nozzle or even worse, rupture the injectors.

Just like the rest of a diesel engines components. These injectors also require lubricating properties that gasoline doesn’t have. This means that as low viscosity gasoline flows through the diesel engine, the components like the fuel pump, delivery system, and valve train are going to rub together and eventually fail. This runs the risk of having metal fillings pumped into the cylinders themselves.

What are the Symptoms of Diesel in a Gas Engine?

If you’ve left the gas station and can’t remember if you’ve put gasoline or diesel in your tank, look out for the following signs:

  • You have difficulty starting the car
  • There’s more smoke than usual coming out of the exhaust pipe
  • The engine gets noisier the more you accelerate

What’s the Best Course of Action?

First of all, if you’ve used the wrong fuel, don’t try to drive away and hope you’ll get home in time. You won’t. Instead, call a tow and have them bring the vehicle to your dealership or an auto shop.

The longer the gasoline is in your diesel engine, the worse it will get. So if you’re already on the road, simply pull over, turn off the ignition, and call a tow.

So a word of advice would be to pay attention at gas stations. Even if you do make a mistake, notice it on time, and take proper action, and DO NOT drive your vehicle.

Richard Reed
I've been a General Manager of a moving company and I've also been a Professional Mover for over 30 years. I've driven flat beds, reefers, dropdecks, moving vans, heavy machinery, etc. In my time as a Mover I've driven over 1,000,000 safe miles. My days of moving and driving truck are past me but The Vehicle Lab allows me to share the knowledge I've gained over the past 40 years.
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