Accidents happen. The size of a gasoline pump nozzle is smaller than that of a diesel pump nozzle. As a result, if you are distracted, it’s easy to pump gasoline into a diesel car. So what do you do if this happens to you? Let’s take a look at three different scenarios:

1) You essentially filled your diesel car’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.

2) You pumped just a little gas into your diesel car

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

3) You pumped more than just a “little” gas into your diesel

Well, it all depends on how much diesel was in the tank before the gasoline was added, and how new and sophisticated the diesel engine is. In a 2007 or newer “clean diesel engine”, any amount of gasoline could harm the sensitive emissions control systems. In older engines with much less sophisticated and sensitive emissions systems, a lightly diluted (say 75 percent diesel/25 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.

How about the other way around, 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. The typical slow-fill diesel pump nozzle is 24 cm 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 into this situation and don’t remember the details of this article, its 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.

Source: Reedman-Toll Fiat