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Oops! I Put the Wrong Fuel in My Car

Gas nozzles

Most of us know what fuel goes into our vehicles, whether it be gasoline, diesel, CNG or electricity, and there’s usually no confusion. When it comes to the liquids, we usually don’t worry about putting in the wrong fuel, and there are even safeguards in place such as fuel inlet restrictors, pump nozzle color coding (which is not consistent from one gas station to the next, however) and pump markings to help us know which nozzle we’ve got in our hands.

On the other hand, you might accidentally put the wrong fuel in your car simply by not paying attention to the pump or due to a lack of proper signage. Jiggle the nozzle just right, and you can defeat the fuel inlet restrictor that is designed to prevent inserting a gasoline nozzle into a diesel filler neck. Hold a diesel nozzle just right, and you can force-feed the fuel into a gasoline vehicle just as easily, although the diesel nozzle will easily fit only older leaded-fuel vehicles. Oops!

The Wrong Fuel Spells TroubleExpensive Diesel Fuel Pumps and Injectors Can be Damaged by The Wrong Fuel.

Even though both gasoline and diesel are made from the same crude oil, they come from different levels in the distillation tower. Gasoline is more volatile and requires a spark for ignition. Diesel is less volatile and requires high-compression to generate the heat required for ignition. Putting the wrong fuel in your car is a problem, because a gasoline engine spark won’t ignite diesel, and a diesel engine’s high compression will ignite gasoline way too early.

It gets worse. Aside from the inconvenience that putting the wrong fuel in your vehicle will cause, it can actually damage the engine and fuel system. When misfueling occurs, you need to take steps as soon as possible to minimize the chances of this happening. If you notice in time, you might be able to get away with simply draining the tank and flushing the fuel system. Depending on the vehicle it may also require replacing the fuel filter and possibly the fuel pump.

On the other hand, if you start the engine and drive for any length of time, you could have expensive repair issues in your future. This is particularly true of diesel vehicles that have been filled with gasoline. Gasoline can ruin some very expensive diesel engine components, such as the fuel pump and fuel injectors, which require the lubricating qualities of diesel. Diesel in a gasoline engine is less likely to cause extensive damage if it’s caught quickly enough. Gasoline mixed with diesel will not burn efficiently, and may result in spark plug fouling, engine misfires and catalytic converter damage. Eventually, the car will not run at all.

Wrong Fuel: What to Do

If you notice the error while in the act of filling the tank, stop fueling immediately. Don’t start your car or even turn on the key; this will start the electric fuel pump and circulate the incorrect fuel throughout the system. Instead, disconnect the battery, push the car off the fueling pad and then have it towed to a repair facility where the fuel tank can be emptied and cleaned.

If you don’t immediately notice the error, and drive the car some distance, pull over and shut off the engine as soon as you recognize your mistake – even if you don’t notice any drivability problems. Have the vehicle towed to a repair shop where the necessary steps to drain, flush and repair the fuel system can be determined.

The longer a misfueled engine runs, the worse the problems are likely to become. The key to minimizing damage is to not run the engine if you know you’ve made a mistake, and to shut off a misfueled engine as soon as you realize a mistake has been made.

Check out all the maintenance parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations or a AAA Approved Auto Repair Facility for routine maintenance and repairs. For more information on how to fix a wrong-fuel situation, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Pixabay.


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