Troubleshooting Fuel Contamination Issues

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Are you using a water-blocking filter, but water is still getting through?

Here are the key questions to investigate:

  • Is the fuel clear and bright or cloudy?
  • Are you using an additive? If so, which one, at what ratio, and how often?
  • Is the entire fuel volume cloudy, or only the bottom around the fuel pick-up?

Fuel Sampling Steps

  1. Take a sample from the water separator. Is the fuel clear and bright, or cloudy?
  2. Take a sample from the top of the fuel tank. Is it clear and bright, or cloudy?
  3. Take a sample from the next fuel delivery. Is it clear and bright, or cloudy?

Checking for Overdosing Issues

  • Is your supplier providing a winter blend fuel?
  • Is the supplier blending the additive? If so, ask for the exact ratio.
  • If the fuel supplier overdosed the fuel—or if you added a cold flow improver to an already treated winter blend—you may have caused the issue.
  • Water reacts to excessive additives, preventing it from being trapped by a water-blocking filter.

Understanding Additive Ratios

It’s crucial to use the correct amount of additive:

  • There are 128 ounces in 1 gallon.
  • If an additive treats 1 gallon per 1,000 gallons of fuel, then 1 ounce treats 7.8 gallons.
  • Did you add more than the recommended amount? More is not better!

Locating and Removing the Problem Fuel

  • Overdosed additives tend to sink to the tank bottom, where the engine’s fuel pick-up is located.
  • Take samples from different points in the tank to determine where clear and bright fuel transitions to cloudy.
  • Pump off and store the bottom fuel until the water naturally separates over time.

Testing for Contamination

To test fuel clarity, use this method: Diesel Fuel Contamination Test.
If the results are inconclusive, a lab test ($200–$400) may be required—contact us for recommendations.

Conclusion

Diesel fuel additives are a cost-effective way to improve engine performance in cold weather. They enhance cold flow without sacrificing power or performance and don’t reduce lubricity or cetane levels like kerosene.

However, excessive additive use can cause contamination issues. Based on our findings, the fuel was likely delivered with too much winter blend additive or was overdosed during treatment.