Know the Sulfur Content of Your Diesel Fuel

Posted: December 16, 2006

It is critical that you know the sulfur content of the fuel that you are using in your diesel engines on the farm.

The sulfur content in “on-road” transportation diesel fuel is regulated by the federal government. The sulfur content has been greatly reduced in recent months and it is critical that you know the sulfur content of the fuel that you are using in your diesel engines on the farm.

Before 1993, the allowable sulfur level in diesel fuel was 5,000 parts per million (ppm). From 1993 until earlier this year, allowable sulfur was 500 ppm. However, starting June 2006, the ultra-low sulfur requirement was implemented which means that the sulfur content must be no higher than 15 ppm for “on-road” transportation fuel. The government is requiring the use of the ultra-low sulfur fuels to reduce the concentrations of sulfur compounds in the environment. However, when sulfur content is reduced in diesel fuel, one consequence is that lubricity of the fuel is greatly reduced. Lubricity of a fuel is the ability of the fuel to provide lubrication to reduce wear between moving parts of the diesel injector pump and the fuel injectors.

Fuel used for “off-road” functions (such as farm, construction, and forestry operations) is exempted from the ultra-low sulfur requirements, at least for the present time. You can still legally use the low sulfur fuel (fuel with 500 ppm sulfur), but the problem is that not all fuel suppliers are carrying both the “on-road” (15 ppm) and the “off-road” (500 ppm) diesel fuel.

How do you know the sulfur content of the fuel being delivered to you? The only way is to ask your fuel supplier for the sulfur content. If he says he doesn't know, insist that he find out and inform you. If your current fuel supplier can only deliver “on-road” diesel fuel to your farm tank, then you have three alternatives: 1) ask your supplier to verify that a lubricity agent has been added to your fuel, 2) add a lubricity agent yourself to the ultra-low sulfur fuel to provide the protection needed in your diesel engines or 3) find a supplier who will deliver “off-road” diesel fuel.

Many different lubricity agents are available at the big-box stores as well as auto supply shops, but these can be quite expensive. A more cost-effective approach is to use biodiesel. Biodiesel has virtually no sulfur content but has excellent lubricity properties. Using just a B1 blend (1 percent biodiesel with 99 percent regular diesel fuel) improves lubricity of ultra-low-sulfur diesel fuel by as much as 65 percent.

Biodiesel is becoming more widely available in many states. To get up-to-date information on where it is available in Pennsylvania, check the web site for the National Biodiesel Board at Click on “Guide to Buying Biodiesel.” Then under the heading of DISTRIBUTORS, click on “Click here for a national map of biodiesel distributors.” Then click on “Pennsylvania” on the map. Make sure that you are buying biodiesel and not just crude, unprocessed vegetable oil. Ask the distributor to provide certification that the biodiesel meets ASTM D6751 standards.



Dennis Buffington
Department of Agricultural and Biological Engineering