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Clean Diesel Technology Yields Significant Benefits in Passenger Vehicles

Diesel Oils

As America searches for a solution to harmful exhaust emissions and its dependence on foreign oil, diesel proponents claim the answer lies in diesel-powered passenger vehicles. The combination of cleaner diesel fuel and significant advances in diesel engine technology over the past two decades has resulted in dramatic improvements in diesel emissions and fuel efficiency, as well as engine reliability and durability.

Perhaps the greatest benefit offered by diesel engines is the fuel efficiency. Because the diesel combustion process is more efficient than gasoline, and because diesel fuel contains more energy per unit volume, diesel engines usually deliver 45 to 60 percent better fuel economy than gsoline engines. For example, the diesel-powered Volkswagen Jetta TDI station wagon, equipped with a five-speed manual transmission, achieves 50 miles per gallon on the highway and 42 mpg in the city. The gasoline version of the same vehicle achieves 31 mpg in the city. According to the Department of Energy, three of the top five highest fuel economy rated passenger cars were diesel-powered in model year 2001.

The fuel economy benefits and reliability offered by diesel-powered passenger cars has earned them a sizable group of devoted owners. "Once you've had one, to go back to a car that gets 15 to 20 miles per gallon is depressing," says Sam Johnson, a mass communications professor at St. Cloud State University in Minnesota and owner of a 2002 Jetta TDI wagon.

A recent study conducted by research firm M.Cubed of Davis, Calif., reports that graduslly increasing the use of clean diesel technology in passenger vehicles to the levels currently seen in Europe could save the state of California 110 million gallons per year by 2030.

"Clean diesel technology is a proven, efficient and readily available solution for California's interest in reducing petroleum consumption," said Allen Schaeffer, executive director of the diesel Technology Forum (DTF), a sponsor of the study. "Other petroleum reduction strategies such as fuel cell-powered cars are not eommercially available and may take 15, 20 or even 30 years of research and development to reach the market. And even then these other technologies would not be as cost effective as diesel or even use less net energy to produce."

Concerns over the effects of carbon-based greenhouse gases on the environment has prompted the Environmental Protection Agency (EPA) to mandate stricter and stricter emissions standards over the years. Because diesel engines offer greater overall efficiency and improved fuel economy when compared to gasoline engines, they emit 30-35 percent fewer carbon emissions. In addition, largely due to cleaner, lower sulfur diesel fuel and improved engine technology, total oxides of nitrogen (NOx) from on-road diesels have dropped 25 percent in the past 10-15 years, while sulfur dioxide (SO2) has dropped 76 percent, coarse particulate matter (PM-2.5) has dropped 35 percent in the last 10-15 years.

While Europe and Japan have recognized and embraced the benefits of diesel-powered passenger vehicles, the United States has the lowesst percentage of diesel-powered passenger vehicles of any industrialized country. Diesel-powered passenger vehicles account for only about one-third of one percent of all U.S. car sales, or about 50,000 of the 16 million vehicles sold last year, while more than one-third of all new vehicle sales in Europe are diesels.

Diesel proponents realize there is great potential for diesel-powered passenger vehicles to thrive in the United States. Diesel-powered light trucks and SUVs are already increasing their presence in the U.S. market, with 435,000 diesel-powered light trucks manufactured for the North American market in 1999.

AMSOIL Synthetic diesel Oils offer unsurpassed protection and performance in large and small diesel engines. Their specially blended long-life formulations resist oxidation and thermal breakdown and eliminate sludge and varnish formation, providing superior wear protection and maximum fuel efficiency for extended drain intervals.

Diesel Fuels Change to Meet New Standards

Diesel Fuel Additives

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 aftertreatment 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 stadards.

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 eletrical 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 Cold Flow Improver (ACF) has been reformulated to provide maximum cold flow capabilities in diesel fuels.

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.