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Diesel Fuels Changing to Meet New Standards

Diesel engine technology is rapidly evolving to meet new emissions standards set by the U.S. Environmental Protection Agency that will go into effect in 2006. Substantial reductions in particulate matter and nitrogen oxides are required of newer engines, resulting in the use of exhaust after treatment devices. These devices are easily poisoned by sulfur, so the pressure is on to further reduce the level of sulfur in diesel fuels. 

The EPA has proposed a cap of 15 parts per million (ppm) of sulfur in diesel fuel beginning in 2006. Currently the level is 500 ppm. This has led to a new class of ultra-low-sulfur diesel fuels (ULSD) with levels of 50 ppm sulfur or lower. 

New emission standards for heavy-duty truck and bus engines begin with the model year 2004 and reflect the provisions of the Statement of Principles (SOP) signed in 1995 by the EPA, The California Air Resources Board (CARB) and the manufacturers of heavy-duty diesel engines. The goal was to reduce nitrogen oxide (NOx) emission levels from highway heavy-duty engines to approximately 2 grams per brake horsepower per hour beginning in 2004. 

Further, in May 2000, the EPA announced proposed emission standards for model year 2007 and later heavy-duty highway engines to regulate diesel fuel and to create emissions standards. 

The ultra-low-sulfur diesel fuel has been proposed as a “technology enabler” to pave the way for advanced, sulfur-intolerant exhaust emission control technologies such as diesel particulate filters and De-Nox catalysts, which will be necessary to meet the 2007 emission standards. 

To get the ultra-low-sulfur levels, refiners perform additional hydroprocessing and higher-severity hydrotreating. While these processes reduce sulfur levels, they also affect other fuel properties. These fuels lose the natural lubricity provided by some of the polar compounds present naturally in the fuel. Low-lubricity fuels can result in premature wear and failure of fuel system components. 

Additionally, severely hydrotreated fuels can suffer from loss of natural antioxidants that help prevent the fuel from forming gums and sludges. A fuel’s antioxidation properties are especially important in today’s fuel systems, where the fuel is exposed to high temperatures. The ultra-low-sulfur fuels also can be more corrosive than conventional fuels, requiring corrosion inhibiting additives. These fuels also can have very low electrical conductivity, causing a safety concern with components such as high-velocity pumps, where fuel can be exposed to significant static electrical charges.

Because of these challenges, some new diesel fuel blending options are being introduced. Gas to liquid (GTL) technology yields diesel blend stocks from stranded gas reserves that might not otherwise make it to market. GTL diesel fuels are desirable blending components because they have the very low sulfur levels as well as high cetane numbers. 

A major percentage of all problems with diesel engines are related to fuel quality, according to Wards Auto World, an e-magazine that offers consumers free auto advice on the Internet. 

Diesel fuel can vary from one shipment to another and from one area to another. Changing vendors or changes suppliers sometimes make to the fuel they sell also bring different qualities of diesel fuel to the market.

Three important components that vary the most in diesel fuel are cetane, weight and viscosity. 

Cetane defines the susceptibility of the fuel to self-ignite. Acceptable cetane levels are between 40 and 45, but few fuel distributors advertise this since each batch may be different. Cetane influences both starting and combustion roughness on an engine. High altitudes and low temperatures call for a greater cetane number of the fuel. 

The weight of the fuel or its gravity plays a role in the heat content of the fuel. Number one is a “lighter” grade and number two is “heavier,” or weighs more per gallon. Number one provides better starting in cold temperatures, but number two has better lubricating qualities and contains more heat units (BTUs) per volume.

The number one fuel is less dense so it becomes thinner when heated than the number two fuel. As the fuel temperature continues to rise, fuel begins to leak through the high-pressure parts of the injection pump causing it to pump less fuel, and that leakage results in a power loss of between one percent and seven percent. 

Diesel fuel treatments increase fuel quality and extend the lives of engines. The only way to be sure of fuel quality is to treat it with fuel additives. 

AMSOIL Diesel Fuel Modifer treats and cleans the fuel system of automotive and light truck diesel engines to improve overall vehicle performance. 

AMSOIL Cetane Boost Additive improves ignition quality and low-temp starting, reduces cranking time, emissions and smoke, provides smoother, quieter operation, increases efficiency and is compatible with AMSOIL Diesel Fuel Additive Concentrate. The Diesel Fuel Additive Concentrate improves fuel economy, extends injector life, increases fuel stability, reduces emissions, improves cold fuel flow and cold startability and controls injector wear in heavy duty applications.