Diesel is the dominant motor fuel used by the commercial transportation sector. In the United States, approximately 94 percent of all freight is moved by diesel power. While diesel fueled engines have a proven track record with respect to power, fuel efficiency and durability, diesel fuel is a major contributor to particulate emissions (PM).

Currently, the sulfur content of most fuel sold in the United States ranges from 350 to 500 parts per million (ppm). In May 2000, theU.S. Environmental Protection Agency (EPA) proposed new, stringent standards designed to reduce emissions from heavy-duty trucks and buses. A key part of the proposal is capping diesel fuel sulfur levels at 15 ppm beginning June 1, 2006, for all highway vehicles powered by diesel fuel. Reducing the sulfur content of diesel fuels provides a direct fuel related PM reduction. More importantly, low-sulfur fuel allows the use of emission control technologies that have been proven effective in controlling PM emissions.

Ultra-low sulfur diesel (USLD) has been mandated by the EPA to be phased into production starting in 2006 as a replacement fuel for the currently available 500 PPM low sulfur diesel motor fuel. The ULSD fuel is highly refined for cleaner combustion and much lower emissions by enabling the use of advanced emission treatment systems. ULSD is compatible with all other diesel fuels and additives that are designed to work in diesel motor fuels. The standard for diesel fuel properties is defined in American Society for Testing and Materials (ASTM) D975-93, Standard Specification for Diesel Fuel Oils. The U.S. Environmental Protection Agency regulation establishing the baseline diesel fuel category is specified in the Code of Federal Regulations, 40 CFR 79.55c, and is based on the ASTM standard. The fuel will run in any conventional diesel engine designed for the ASTM D-975 diesel fuels.

All dispenser pumps must be labeled to indicate the sulfur level and designation of the fuel. (e.g. S15 diesel or S500 diesel.) For example, any dispenser with S500 (500 ppm of sulfur) diesel fuel must declare that the fuel is not suitable for fueling model year 2007 and later vehicles. All diesel dispensers must be appropriately labeled on June 1, 2006.

The color of a diesel fuel is not related to its performance. As long as the fuel meets specifications, it will perform well in diesel engines. The natural color of diesel fuels has traditionally varied from colorless to amber. As refinery processing of the diesel fuel increases to remove the sulfur, the color has tended to get lighter and the diesel can change color. When it changes color the diesel is typically light in tone, but can be green, orange or pink. Sometimes it might show a slight fluorescence when held up to light. Such a change in color does not affect the quality of the diesel.

While the Department of Commerce has regulatory oversight for most motor vehicle fuels used in Wisconsin, the department does not have regulatory oversight of the federal ULSD requirements.

The Internet URLs below provide compliance dates and other related ULSD helpful references:

• www.clean-diesel.org/ (This web site includes examples of dispenser labels)
  
• www.epa.gov/cleandiesel/presentations/hwyulsdrule.pdf
  
• www.dieselforum.org/meet-clean-diesel/what-is-clean-diesel/new-technologies/ultra-low-sulfur-diesel

-- Sheldon Schall

The newsletter is issued electronically every other month.

Please send comments or questions to Barbro McGinn, editor.