Accidental Mixing of Gasoline and Diesel

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Accidental Mixing of Gasoline and Diesel

Recently a customer of ours had a problem where their fuel supplier mistakenly unloaded 3000 gallons of ULSD#2 into their unleaded gasoline tank that contained about 700 gallons of gas.

When this happens there is very little that you can do beyond having the tank completely pumped out and then replacing the fuel.

Diesel in gasoline will generally cause the engine to either not start at all of run very poorly.

There is no acceptable amount of diesel in gasoline, although the engine will likely run if the amount of diesel is only 1 or 2% of total.

Gasoline in diesel is an equally serious problem. Even very small amounts (1%) can affect the flash point of the fuel significantly. This lowering of the fuels flash point can have catastrophic effects on the engine as it affects the fuels ignition and can also strip the lubricating ability of the diesel fuel, quickly damaging pumps and injectors.

In the past truck drivers would sometimes add a small amount of gasoline to their diesel fuel to try and prevent gelling. Many of these drivers feel that at long as the engine kept running it must be a good idea. It has never been a good idea for the reasons mentioned above and the fact that the engine kept running does not take into account increased wear and failures that happened days, weeks, or months later.

The addition of Ethanol to most gasoline available today simply makes using any amount of gasoline in diesel a very dangerous proposition.

In general, you should have this contaminated fuel taken away by a company licensed to handle it.

If you ever get gas in your diesel or diesel in your gas, the safest thing is to immediately without running the engine, have the tank drained and then replace with the correct fresh fuel.

Please let us know what you think and any experiences you may have had.

Diesel Doctor


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Last modified: 04/06/09
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