Winter Diesel Fuel


Is there such a thing? Yes.

Wondering about the different grades of diesel fuel, and what makes winter diesel fuel so special? Today, we’ll cover the different types of fuel, and clarify when winter diesel fuel should be used.

Diesel fuel is principally a blend of petroleum-defined compounds, called middle distillates. These compounds are heavier than gasoline, but lighter than lubrication oil, and may contain additives. There are four grades of diesel fuel: Low Sulfur 1-D and Low Sulfur 2-D (rated for on-highway use), and High Sulfur 1-D and High Sulfur 2-D (rated for off-highway use). Regardless of sulfur content, 1-D grade diesel is recommended for low ambient temperatures, and is a lighter, lower-BTU more volatile fuel that is almost kerosene-like. 2-D grade fuel is less volatile, and is recommended for more moderate climates.

1-D grade diesel fuel and kerosene are NOT the same thing, despite being similar in their characteristics. According to ASTM-D 975, 1-D diesel fuel is rated for use in engine equipment, while kerosene is used in heating appliances. Kerosene and 1-D diesel fuel have different specifications. Kerosene can be classified as either being 1-K or 2-K kerosene. 1-K kerosene should not be assumed to meet 1-D diesel fuel standards, nor should 1-D diesel fuel be assumed to meet 1-K kerosene standards. If you want to interchange these fuels, check with your fuel supplier. In 1994, the IRS issued regulations on the tax exemption of diesel fuels which may affect product selection.

Winterized diesel fuel is 2-D grade diesel which has been modified to permit its use at lower ambient temperatures. Generally, this is achieved by blending 1-D and 2-D grades of diesel fuel together. The amount of improvement realized will depend upon the physical and chemical properties of the 1-D diesel used. 1-D diesel can be blended with 2-D to lower the cloud point. At temperatures below the 2-D cloud point, wax precipitates from the fuel mix, and is much more difficult to re-dissolve with the addition of 1-D. Therefore, 1-D should be added at temperatures above 2-D’s cloud point. If the wax has precipitated, heating and mixing will be required. The final blend will most likely have a slightly lower cloud point, and will therefore form wax crystals and begin to gel at a lower temperature. Gelling is a thickening of the fuel caused by wax crystals, which form as the fuel cools down. This gelled fuel is difficult to pump, and the wax crystals can clog fuel filters, starving the engine.

IMPORTANT: Gasoline should not be used to dilute diesel fuel because the mixture is much more flammable and has greater explosive potential than either gasoline or diesel fuel alone.

Wondering why you’d need winterized diesel fuel? Well, when diesel fuel is produced at the refinery, its ultimate destination is unknown, so it is blended to meet a generic temperature requirement. Since the winter temperature requirements vary widely in different parts of the country, diesel fuel must be modified and additized locally to meet the specific needs of a region. With respect to performance, high-sulfur and low-sulfur diesel behave the same way. Both can be blended with additives to improve low temperature performance. Low sulfur diesel tends to be more difficult to treat due to the types of wax compounds and higher water content typically present.

Wondering what additives are used to improve the performance of blended diesel? We’ll cover that in another post. In the meantime, if you have any questions about diesel fuel or diesel fuel blends, contact Clean Fuels Associates today.