MFA OIL

The move to low-sulfer fuels hits pace
By Don North

During the early 1970s the Environmental Protection Agency imposed emissions standards on gasoline engines. The advent of unleaded gasoline and catalytic converters signaled the beginning of a 30-year period during which many changes in fuels and vehicles would be aimed at reducing air pollution.

This year is another big year for air pollution control as EPA mandates reduction of sulfur levels in both gasoline and diesel fuel. Although the principal reasons for these reductions are improved efficiency and life of catalytic converters, lower sulfur levels also will reduce the emissions of sulfur dioxide. As an added advantage, experience tells us that cleaner fuel extends engine life.

Gasoline

In 2005, the EPA reduced the maximum sulfur limit in all gasoline at the refinery level from 500 ppm (parts per million) to 30 ppm. The EPA estimated it would take over a year to reduce sulfur content to 30 ppm at the retail pump. Currently, average sulfur content at the retail gasoline pump is under 100 ppm. This low-sulfur gasoline program has been working very well.

Lowering the sulfur content in gasoline will not reduce the miles per gallon of a gasoline engine or impair performance. With low-sulfur gasoline helping to extend the life of the catalytic converter and engine, you could see improved performance over the life of the engine.

Diesel

The EPA, maintaining that reduction of sulfur content in fuels would decrease nitrous oxide and particulate matter emissions to the atmosphere, introduced lower sulfur requirements for diesel fuels in 1993. The first mandate was that all on-road diesel fuel decrease from a maximum of 5,000 ppm sulfur to 500 ppm. That mandate is still in effect today, and the fuel is sold as “low-sulfur” diesel fuel.

In June 2006, the EPA has initiated a new mandate that refineries will be required to produce a new, lower-sulfur diesel fuel known as “ultra-low sulfur” diesel. Ultra-low sulfur will have a maximum sulfur content of 15 ppm.

Diesel engines built in 2007 and later will require ultra-low sulfur due to the catalytic exhaust emission control device (particulate trap). This device will be damaged if diesel fuel with sulfur levels above 15 ppm is used. EPA and state agencies will monitor refineries and fuel retailers for sulfur content to assure the end user that ultra-low sulfur does not exceed 15 ppm.

Sulfur plays an important role in the lubricity of diesel fuel, providing lubrication of the injection system to resist wear. All ultra-low sulfur will have a lubricity additive injected at the terminal, but diesel engine makers think more lubricity may be necessary to assure adequate protection.

One solution to the loss of lubricity in ultra-low sulfur is to use biodiesel. Biodiesel has no sulfur content and, in blends as low as B-2, has proven to be an excellent lubricity agent. Biodiesel can be used in both older and newer engines. Most over-the-counter, after-market additives, on the other hand, have not been approved for use in 2007 and newer diesel engines. Unapproved fuel and engine oil additives can damage the particulate trap.

Desulfurization of diesel fuel reduces energy content, resulting in a slight loss of horsepower and/or miles per gallon in some diesel engines. All early testing of ultra-low sulfur indicates that use of a “premium” ultra-low sulfur will benefit the end user.

EPA has asked retailers to start selling new ultra-low sulfur by October 2006. Ultra-low sulfur will be introduced as a second product, with low-sulfur diesel still available for sale.

Retailers can sell low-sulfur diesel for on-road use to owners of 2006 and older diesel-powered vehicles until 2010. However, ultra-low sulfur must be used in vehicles made in 2007 onward and can be used in older model diesel vehicles without any harmful effects. The retail dealer must clearly identify diesel fuel pumps as low-sulfur diesel or ultra-low sulfur, but since most diesel fuel pumps are self service, ultimately it will be the vehicle operator’s responsibility to make sure to use the correct pump.

Eventually, the EPA mandates will affect off-road diesel engines as well. Off-road diesel manufacturers will be required to produce ultra-low sulfur engines by 2010. All diesel fuel must be ultra-low sulfur by 2014.

Don North is director of product development and lubricant sales at MFA Oil.