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Gas in Diesel EngineMuscle memory is often a much stronger force than you may think. If you’re used to driving a gas-powered car, you may accidentally go to the wrong refueling pump in your diesel vehicle. And depending on how quickly you realize it, that kind of error will fall somewhere within the range of “minor annoyance” and “destroyed engine.”

Gas vs. Diesel: What Makes Them Different?

Gasoline requires a spark to ignite. In an engine’s combustion chambers, spark plugs light the gas, creating an explosion that pushes down the pistons. Diesel, on the other hand, does not require a spark to ignite, which is why there are no spark plugs in diesel-based engines. Instead, diesel fuel relies on compression alone to generate that explosive burn.

The Consequences of Gas in Diesel Engines

Just as an example, let’s say that you put a few gallons of gas in your diesel tank. Even if the tank is 99% filled with diesel, that tiny contamination of gas drops the diesel’s combustion temperature, leading to premature ignition.

In turn, you’ll notice the following:

  • Your engine running rough
  • A massive drop in power
  • Lots of blue or black smoke coming from the exhaust
  • Strange clattering noises
  • Engine stalling (and possibly not starting again)

Another disastrous consequence is reduced lubrication since diesel acts as a lubricant in engines to keep their internals moving smoothly.

Fuel pumps and injectors will likely fail, as well. Pistons and cylinders will get hot spots and overheat, valves can stick and amass carbon buildup, and fuel filters and lines will become clogged.

If you were to accidentally put a full tank of gasoline into your diesel vehicle, it would only accelerate the rate at which these catastrophes happen. And even if the engine manages to run, failures will still stack up fast.

What to Do

In the accidental event that you put gasoline in your diesel tank, do not start the engine. (But if you have, shutting it off quickly enough may be able to prevent catastrophic damage.) Instead, have your vehicle towed to a reputable repair shop.

There, the car’s fuel tank will be emptied and cleaned. Though it’s possible its lift pump may have survived the encounter with gasoline, there’s no guarantee, which means, in most cases, it will have to be replaced.

From there, the shop will clean the vehicle’s fuel supply lines, replace its fuel filters, inspect (and likely replace) its fuel injectors, clean its fuel rails, and possibly replace its injection pump as well.

How to Avoid Misfuelling

Everyone makes mistakes, but you can reduce the chances of misfuelling in the future with these few simple tips:

  • Add a warning label to your fuel cap that reads, “Diesel Only”
  • Use color-coded key rings and labels to differentiate between your gas and diesel vehicles
  • Put corresponding color-coded labels on your fuel caps
  • Diesel pumps are almost always a different color than gas pumps, so make a habit of differentiating while at the station

A little precaution goes a long way. Fuel prices are high enough, but a mixup between gas and diesel can result in the most expensive tank of fuel you’ve ever needed.

Summary: Accidentally putting gasoline in a diesel vehicle can completely ruin its engine. Vital components will be destroyed, and those that remain will require thorough cleaning by an experienced repair facility.



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