Mercedes has a new, technologically-advanced series of gasoline engines, capable of running on a “lean-burn” mode that both reduces emissions and increases fuel efficiency—but they’re not coming to America because the gasoline here isn’t clean enough for the Silver Arrow’s refined tastes.
The problem is that American gasoline contains too much sulfur—as much as 80-95 parts per million across the country. Mercedes needs a sulfur content of less than 50ppm to function correctly, due to the leaner fuel-to-air ratios that allow them to run more efficiently than conventional gasoline engines. The extra quantities of sulfur would overwhelm the trap that captures oxides of nitrogen from the exhaust stream. With the lean-burn combustion cycle, fuel efficiency increases 10%.
Mercedes has fared better with their low-sulfur diesel engines, as U.S. regulations have limited sulfur content in diesel to 15ppm. But in Europe, gasoline sulfur content has been regulated to “almost zero,” according to Mercedes engineers. The EPA is currently evaluating the impact of lower-sulfur gasoline. Sulfur by itself does not actively impact fuel economy.
Mercedes will still sell the four- and six-cylinder engines in America, but simply without the lean-burn capabilities. One of these engines, called BlueDirect in the U.S., is the direct-injection 3.5-liter V6 which will make it across the 2012 C-Class, E-Class, M-Class, and SLK. It still gets a commendable 21-mpg with 302 hp and 273 lb-ft of torque. The C-Class also gets a new 1.8-liter four-cylinder that also has direct injection but features turbocharged fury: at 201 horsepower and 229 lb-ft of torque, and 24-mpg.
Lastly, Mercedes is equipping the CL-Class with yet another direct-injection powerhouse, this time a V8: with an MPG rating of 15/23, the twin-turbo 4.6-liter eliminates the gas guzzler tax for the CL550, while producing 429 hp and 516 lb-ft of torque.
But take heart, Americans: our gasoline may be filthy compared to the fine, floral bouquets of the Continent, but it’s not just an American issue: Mercedes won’t be able to sell these engines with lean-burning cycles in markets in Asia and Africa. Ideally, the engineers at Mercedes would like to see a global standard for sulfur, so we won’t feel like we’re not worthy of Mercedes’ gasoline snobbery.
[Source: Ward's Auto]