Mercedes-Benz will add three clean diesel SUVs to its lineup this fall. The 2009 GL320, ML320, and R320 (from left to right) will be available in all 50 states as diesel-powered BlueTEC models.
These new BlueTEC models are a continuation of the company's bullish stance on high-tech diesel engines. Because of their basic design, diesels are inherently more economical than comparable gasoline engines, but they also have "dirtier" exhaust emissions in terms of nitrogen oxide and soot particles.
Mercedes' E320 BlueTEC midsize sedan, introduced in late 2006 as a 2007 model, was the first passenger car in the U.S. optimized to use the newly mandated ultra-low-sulfur diesel fuel (or ULSD). ULSD, or "clean diesel," has a significantly lower sulfur content vs. the previous U.S. standard for diesel fuel (15 parts per million versus 500 ppm, respectively). ULSD enables the use of a new generation of emissions control technologies that have the capability to make diesel engines run as clean as comparable gasoline engines.
Chief among these state-of-the-art components is the particulate filter. This device is mounted midstream in a diesel vehicle's exhaust system to trap soot particles, and uses the heat of the engine's exhaust gases to incinerate the trapped particles before they can exit the vehicle. The E320 BlueTEC's 3.0-liter turbodiesel V6 utilized a particulate filter and other emissions-reducing technologies to achieve Federal Bin 8 emissions standards. Mercedes introduced GL-, M-, and R-Class SUVs using a version of this engine for the 2007 model year. However, none of these models met the emissions requirements to operate in California, Maine, Massachusetts, New York, and Vermont, which adhere to more-stringent "Bin 5" standards.
AdBlue Joins BlueTEC
Mercedes' new BlueTEC vehicles use AdBlue, an exhaust emission treatment system that reduces nitrogen oxide emissions.
The new 2009 BlueTEC SUVs meet 50-state emissions requirements, thanks to the addition of Mercedes' AdBlue technology. AdBlue is an exhaust emission treatment system that reduces nitrogen oxide emissions.
AdBlue-equipped vehicles carry an aqueous urea solution in a separate on-board tank. This AdBlue solution is injected into the exhaust stream, where it is heated by the exhaust gases and broken down into its constituents of water and urea. From 170 degrees Celsius (338 degrees Fahrenheit), the urea is converted to ammonia. The ammonia is then stored in the catalytic converter, and converts up to 80 percent of the nitrogen oxides in the exhaust stream to harmless nitrogen and water before they can enter the atmosphere.
The engine management system meters the AdBlue solution injection to maintain the proper level of ammonia in the catalytic converter.
M-Class and R-Class models carry an AdBlue tank with a capacity of about 7 gallons. The GL-Class has a tank that holds about 8.5 gallons. The AdBlue system is designed to require no driver involvement. Under normal driving conditions, Mercedes says the tank need only be filled at the regular 10,000-mile dealer service intervals.
On the Road
We recently had the opportunity to test all three of these next-generation diesel SUVs and were impressed by their on-road performance. Mercedes engineers have been able to filter out virtually every trace of the two primary diesel bugaboos: smelly exhaust fumes and clattery engine and exhaust noises. We noticed only a hint of engine "clatter" at idle. The GL320, ML320, and R320 are all rated at 210 horsepower. That doesn't sound like a lot when you're lugging around about 5,000 pounds of SUV, but the torque figure rating--a hefty 398 lb-ft at just 1,600-2,400 rpm--tells the true story. The BlueTEC diesel's low-end power gives these vehicles perfectly adequate pickup in most driving situations. In all, the performance of these engines burnishes Mercedes' premium-brand credentials, and should help erase the bad memories of the noisy, smelly diesel passenger vehicles of days gone by.
Other than their powertrains, the BlueTEC SUVs are virtually identical to their mainstream gasoline-powered counterparts. While the GL-Class and the R-Class are mostly carried over, the 2009 M-Class receives some interior materials upgrades and exterior styling updates that include a revamped front end, larger mirrors, and a new rear bumper.
Mercedes claims that its BlueTEC diesels are 20 to 33 percent more economical than a comparable gasoline engine. Though we didn't have a chance to measure fuel economy, Mercedes lists figures of 18 city/24 highway for the ML320 and R320, and 17/23 for the GL320. By comparison, the Chevrolet Tahoe Hybrid is EPA-rated at 20 city/20 highway with 4WD, and 21/22 with 2WD. The Lexus RX400 hybrid is rated at 26 city/24 highway. As these figures suggest, diesels are at their best in highway cruising.
Adding It Up
The current non-AdBlue diesel models command a premium of $1,000 over their gasoline-powered equivalents. Mercedes has not yet released full pricing for the '09 BlueTEC SUV trio, but the company is aiming to keep the price premium close to that $1,000 figure. Mercedes representatives hasten to point out that the surcharge for gas-electric hybrid technology in competitive SUV models is around $3,000.
The three new 2009 BlueTEC SUVs will be 50-state certified, unlike Mercedes' BlueTEC E320 (above). Introduced for 2007, E320 wasn't cleared to operate in states with stringent emissions requirements like California, Maine, Massachusetts, New York, and Vermont.
Diesel or not, it's clear that there are risks in developing new fuel-saving technologies. Despite the recent fuel price setbacks, Mercedes remains dedicated to further research and development of diesel powertrains, but is also focusing on other avenues for increased efficiency that don't compromise the high-end status of the brand. Two gasoline-electric hybrids, the ML450 BlueHYBRID SUV and the S400 BlueHYBRID large sedan, are slated for release in 2009 as 2010 models.
Diesel-electric hybrids might also be in Mercedes' future, judging by a recent concept version of its forthcoming GLK-series compact SUV. The Vision GLK BlueTEC HYBRID uses a new 2.2-liter four-cylinder diesel coupled with a hybrid module for a combined 224 horsepower and 413 lb-ft of torque. Mercedes claims the concept can achieve 40 mpg while meeting the strictest emissions standards.
07.24.2008
