Opps – Pumping Gasoline into a Diesel Vehicle

The size of a gasoline pump nozzle is smaller than that of a diesel pump nozzle.  This means the filling port of a diesel vehicle is larger than a gasoline one.  As a result, if you are distracted, it’s easy to pump gasoline into a diesel car.  So what do you do if this accidently happens to your car?   We asked the service staff at Performance in Woodbury, NJ, a full-service Dodge, Chrysler, Jeep, Ram dealer  and they suggested three different scenarios:

  1. Just a little gasoline was pumped into your diesel vehicle

If this is the case and you caught yourself before more than a dollar or so was pumped in, you are probably OK. Immediately, stop pumping the gasoline, of course, and then fill the rest of the tank up with diesel fuel.  The diesel will dilute the gasoline to such a degree that it will make little difference to the engine

  1. More than just a “little” gas into your diesel

If you pumped in several gallons of gasoline, well, it all depends on how much diesel fuel you can use to dilute it, and how new and sophisticated the diesel engine is.   In a 2007 or newer “clean diesel engines”, any amount of gasoline may  harm the sensitive emissions control systems.  In older engines with much less sophisticated and less sensitive emissions systems, a lightly diluted (say 85 percent diesel/15 percent gasoline) mix would probably work with little or no detriment. It might simply result in less engine power and perhaps a bit more engine noise.

  1. You filled your diesel vehicle’s tank with gasoline

If this has occurred, then stop filling the car and arrange to have your car towed to a service station and have the tank drained.  Don’t try to start the engine!  Diesel engines operate at very high compression and having a volatile fuel like gasoline being pumped into the combustion chambers is probably going to damage the engine.  

What if the reverse occurs, putting diesel fuel in a gasoline engine?

Fortunately, this one is difficult to accomplish.  Since the filler nozzles on diesel fuel dispensers are larger than those on gasoline pumps, it doesn’t happen as often because immediately “something seems wrong.”  Here are the technical details: The typical slow-fill diesel pump nozzle is 24 cm in diameter and fast-fill truck nozzles are even larger, well over 25 cm, while the nozzle for a gasoline pump is about 21 cm. So, a large diesel spout won’t fit in a narrow gasoline filler neck, so most people catch themselves before they mix up the fuels.

If you ever do get caught in this situation and don’t remember the details of this article, it’s always a good idea to call your local dealer and ask the service manager what he/she recommends.  Today’s newer cars and trucks are very sensitive to fuel issues so it may be best to consult a factory-trained professional for advice.


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