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Fuel Station Catastrophe

What to do if you fill your diesel with gasoline

Jason Sands
Jan 1, 2013
Photographers: Jason Sands
Perhaps one of the biggest “Uh, oh!” moments a diesel owner can have is when he realizes he has just put gasoline in his diesel’s tank. Often, this can happen when a vehicle is lent to a friend or family member who isn’t used to filling up with diesel fuel. In all cases, nothing good can happen when a diesel tank is filled with gasoline, with the effects ranging from bad to worse.
Photo 2/7   |   1301dp 01 Fuel Station Catastrophe Jason Sands Fueling With Gasoline
How Much is Too Much?
A lot of people wonder how much gasoline you can actually put in a diesel tank before it has detrimental effects, and the correct answer to this is: very little. Many years ago, people used to mix roughly 1 gallon of gas in with about 20 gallons of diesel fuel in extremely cold climates to keep the fuel from gelling, but with today’s fuel heaters and additives, this practice is no longer very common. Even if you accidentally pour just a couple gallons of gasoline into your tank, you should drain it immediately, just to be safe.
Photo 3/7   |   While most fuel fill pumps are labeled green (indicating diesel fuel), we’ve also seen yellow, or handles with the rubber ripped off. Make sure to also check at the actual pump to ensure that it is, in fact, diesel fuel.
What Can Happen?
When gasoline is introduced into a compression-ignition engine system designed to run on diesel fuel, problems aren’t far behind. Diesel fuel is used to lubricate and cool the high-pressure components of the fuel system, something gasoline does not do properly. Gasoline also burns at a higher temperature, causing the engine to run much hotter. Finally, a high octane number equals a low cetane number, which means the gas may not ignite at all, and the engine will just quit running. If the engine does run, the hotter-burning gasoline, with its lesser lubricating properties, can take out your injection pump, injectors, and even a piston.
Photo 4/7   |   Have a bunch of gas cans around and forget which one has which type of fuel in it? Pour a little in a cup or can; the gasoline will quickly evaporate, while the diesel will be very slow to disperse.
The Bottom Line
If you put gasoline in your diesel, you should drain it. Don’t try to run the vehicle—even for a short distance or a short while. It’s just not worth the damage that may occur. While the $400 to $800 price to drain and clean a tank may sound steep, it’s just not worth risking the well-being of your vehicle.