How Clean Diesel Fuel Works

Ultra-Low Sulphur Diesel Fuel Vehicles

Mercedes-Benz' Bluetec diesel technology is available in the GL320, ML320, and R320 [from left to right].

Concerns about the world's oil supply and ever-rising fuel prices have brought a renewed focus on diesel's superior fuel economy. Because of their unique engine design, diesel engines are typically 20 percent to 40 percent more fuel-efficient than comparable gasoline engines. A 2004 EPA study concluded that if just one-third of light-duty trucks in the U.S. were operated with state-of-the-art diesel engines, the country would save 1.4 million barrels a day -- equal to the amount the USA currently imports from Saudi Arabia. A recent J.D. Power study predicts that diesel sales will trend upward, comprising 11.8 percent of the market in 2015 as opposed to the 3.6 percent they comprise today.

The transition to clean diesel will have a definite impact on future consumer choices, as automakers formulate strategies and introduce new passenger vehicles to take advantage of this shifting market. Mercedes-Benz has recently debuted four new 2007 models (one car and three SUVs) that utilize the company's new Bluetec diesel V6 engine. DaimlerChrysler has also announced its Jeep division will offer the new Mercedes-built diesel V6 in the 2007 Jeep Grand Cherokee. These vehicles meet the EPA's BIN 8 emissions requirements, making them legal for sale in 45 states. (California, Maine, Massachusetts, New York, and Vermont adhere to stricter BIN 5 emissions requirements for passenger vehicles.)

For the 2008 model year, Mercedes plans to equip its diesel engines with a urea-injection system, which it has dubbed AdBlue. The system adds measured quantities of a urea-based solution into the exhaust stream to help reduce nitrogen oxide emissions. The AdBlue system should enable Mercedes' future diesels to reach BIN 5 emissions requirements for 50-state legality.

More new products are on the horizon. Honda has announced a next-generation diesel engine that it plans to release in the U.S. by 2009. The Honda engine will utilize a dual-stage catalytic converter that converts nitrogen oxide exhaust emissions into ammonia and then into harmless nitrogen gas. Honda claims the new engine will meet BIN 5 requirements and achieve emissions as clean as a gasoline engine's. General Motors and Volkswagen, among other manufacturers, are expected to launch new diesel-powered models within the same 2009 timeframe. Some industry analysts have likened the current ULSD changeover to the mid-1970s changeover from leaded to unleaded gasoline, which was implemented in part to enable the use of emissions-reducing catalytic converters. Proponents of ULSD are hopeful that the switch to clean diesel will have a similar positive impact on the environment.

Diesel and Hybrid Comparison

Like previous diesel passenger vehicles, the new generation of ULSD-fueled vehicles will cost more than their non-diesel counterparts. However, the sticker-price hike should be less than the current premium for gas/electric hybrid technology. Mercedes-Benz's 2007 Bluetec diesel models start at $1000 more than their gasoline siblings. Most 2007 hybrid vehicles demand a premium of $2500-$3700 over the comparable non-hybrid versions.

In the arena of fuel economy, let's look at how the Mercedes diesels stack up against a pair of comparable luxury gas/electric hybrid vehicles. The Mercedes-Benz E320 Bluetec sedan is EPA rated at 26 mpg city/37 mpg highway. The 2007 Lexus GS 450h sedan, while it provides slightly better acceleration, is rated at 25/28 mpg. The Mercedes-Benz ML320 CDI sport-utility vehicle is rated at 21/27 mpg. The 2007 Lexus RX 400h hybrid SUV is rated at 31/27 mpg -- more efficient in city driving, but the same on the highway.

Judging from these early examples, it appears that the next generation of diesel vehicles will be viable competitors in the automotive marketplace. There are still challenges to overcome, but the potential benefits are clear: ULSD and the new emissions-reducing technology that it facilitates will help make the air cleaner and healthier for everyone.