Diesel Fuel Analysis: Importance of Fuel Type

When submitting a diesel fuel sample for laboratory testing and analysis, it can be easy to assume that all diesel fuel is essentially the same and that it is not important to identify its grade. However, failure to do so can result in inaccurate test results and unnecessary alerts due to differences in the grades of the diesel fuel.

Distinguishing Diesel Fuel Types

According to ASTM D0975-22a, “Standard Specification for Diesel fuel,” the major types of diesel fuel are #1 and #2, with three grades each depending on the amount of sulfur present. Diesel fuel #2 the most common and is a general purpose fuel with a wide variety of applications. In the absence of special conditions, this is generally the most applicable fuel to use as it is cost-effective and offers better fuel mileage vs diesel fuel #1. Diesel fuel #1 is a special purpose fuel with a lower volatility that can withstand a lower temperature before gelling. This can be useful in lower temperatures and it can be used to make winter diesel blends.

In addition, both types of fuel are split into three grades each based on parts per million of sulfur content.

  1. S5000 (sometimes called high sulfur fuel) contains a maximum of 5000 ppm of sulfur
  2. S500 (sometimes called low sulfur fuel) contains a maximum of 500 ppm
  3. S15 (sometimes called ultra low sulfur fuel or ULSDF) contains a maximum of 15p pm of sulfur
    1. Learn more about verifying ppm specs in ultra low sulfur diesel fuel here

Differences in Diesel Fuel Testing

The differences between #1 and #2 diesel fuel can be seen in several laboratory tests. In particular, diesel fuel #1 will have lower results for Viscosity, Cloud Point, Pour Point and Distillation in relation to diesel fuel #2. Correctly identifying the fuel type will ensure that the analysis results are compared to the correct standards during analysis. This will help to determine if the fuel conforms to its specification, remove potential false alarms and ensure that the reported condition of the fuel is accurate.

Download our Complete Testing List here for more information on fuel testing offered by POLARIS Laboratories®

You can read more on the effects of ultra-low sulfur diesel fuel on viscosity in our Technical Bulletin here

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Published March 10, 2023